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 $67.59   10.860%   $74.9303   $74.93   $74.95   $74.90  
  Purchase #2 $203.84   4.488%   $212.9883   $212.99   $213.00   $213.00  
  Purchase #3 $219.50   10.155%   $241.7902   $241.79   $241.80   $241.80  
  Purchase #4 $165.37   13.184%   $187.1724   $187.17   $187.15   $187.20  
  Purchase #5 $37.57   9.482%   $41.1324   $41.13   $41.15   $41.10  
  Purchase #6 $200.84   9.506%   $219.9319   $219.93   $219.95   $219.90  
  Purchase #7 $146.46   10.842%   $162.3392   $162.34   $162.35   $162.30  
  7 purchase totals = $1,041.17       $1,140.2847   $1,140.28   $1,140.35   $1,140.20