Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $88.35   6.765%   $94.3269   $94.33   $94.35   $94.30  
  Purchase #2 $181.97   11.860%   $203.5516   $203.55   $203.55   $203.60  
  Purchase #3 $231.64   7.404%   $248.7906   $248.79   $248.80   $248.80  
  Purchase #4 $200.90   7.433%   $215.8329   $215.83   $215.85   $215.80  
  Purchase #5 $97.65   6.505%   $104.0021   $104.00   $104.00   $104.00  
  Purchase #6 $134.57   4.846%   $141.0913   $141.09   $141.10   $141.10  
  Purchase #7 $88.97   13.279%   $100.7843   $100.78   $100.80   $100.80  
  7 purchase totals = $1,024.05       $1,108.3797   $1,108.37   $1,108.45   $1,108.40