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 $87.88   6.456%   $93.5535   $93.55   $93.55   $93.60  
  Purchase #2 $211.77   6.295%   $225.1009   $225.10   $225.10   $225.10  
  Purchase #3 $63.51   8.483%   $68.8976   $68.90   $68.90   $68.90  
  Purchase #4 $106.30   11.666%   $118.701   $118.70   $118.70   $118.70  
  Purchase #5 $200.42   6.815%   $214.0786   $214.08   $214.10   $214.10  
  Purchase #6 $53.77   7.409%   $57.7538   $57.75   $57.75   $57.80  
  Purchase #7 $240.50   5.832%   $254.526   $254.53   $254.55   $254.50  
  7 purchase totals = $964.15       $1,032.6114   $1,032.61   $1,032.65   $1,032.70