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 $94.60   7.773%   $101.9533   $101.95   $101.95   $102.00  
  Purchase #2 $193.69   10.867%   $214.7383   $214.74   $214.75   $214.70  
  Purchase #3 $61.93   10.402%   $68.372   $68.37   $68.35   $68.40  
  Purchase #4 $156.85   6.360%   $166.8257   $166.83   $166.85   $166.80  
  Purchase #5 $237.83   8.306%   $257.5842   $257.58   $257.60   $257.60  
  Purchase #6 $219.67   9.263%   $240.018   $240.02   $240.00   $240.00  
  Purchase #7 $126.40   4.392%   $131.9515   $131.95   $131.95   $132.00  
  7 purchase totals = $1,090.97       $1,181.4430   $1,181.44   $1,181.45   $1,181.50