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 $94.50   7.109%   $101.218   $101.22   $101.20   $101.20  
  Purchase #2 $205.26   3.179%   $211.7852   $211.79   $211.80   $211.80  
  Purchase #3 $136.28   11.172%   $151.5052   $151.51   $151.50   $151.50  
  Purchase #4 $62.72   12.637%   $70.6459   $70.65   $70.65   $70.60  
  Purchase #5 $193.68   4.788%   $202.9534   $202.95   $202.95   $203.00  
  Purchase #6 $67.31   10.829%   $74.599   $74.60   $74.60   $74.60  
  Purchase #7 $238.35   10.260%   $262.8047   $262.80   $262.80   $262.80  
  7 purchase totals = $998.10       $1,075.5114   $1,075.52   $1,075.50   $1,075.50