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 $200.35   3.600%   $207.5626   $207.56   $207.55   $207.60  
  Purchase #2 $11.26   6.743%   $12.0193   $12.02   $12.00   $12.00  
  Purchase #3 $212.37   7.555%   $228.4146   $228.41   $228.40   $228.40  
  Purchase #4 $233.26   6.428%   $248.254   $248.25   $248.25   $248.30  
  Purchase #5 $80.25   13.742%   $91.278   $91.28   $91.30   $91.30  
  Purchase #6 $147.67   4.204%   $153.878   $153.88   $153.90   $153.90  
  Purchase #7 $81.36   3.657%   $84.3353   $84.34   $84.35   $84.30  
  7 purchase totals = $966.52       $1,025.7418   $1,025.74   $1,025.75   $1,025.80