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 $87.47   5.244%   $92.0569   $92.06   $92.05   $92.10  
  Purchase #2 $151.51   11.119%   $168.3564   $168.36   $168.35   $168.40  
  Purchase #3 $165.28   9.481%   $180.9502   $180.95   $180.95   $181.00  
  Purchase #4 $151.60   10.506%   $167.5271   $167.53   $167.55   $167.50  
  Purchase #5 $121.94   3.868%   $126.6566   $126.66   $126.65   $126.70  
  Purchase #6 $38.85   6.187%   $41.2536   $41.25   $41.25   $41.30  
  Purchase #7 $91.68   7.717%   $98.7549   $98.75   $98.75   $98.80  
  7 purchase totals = $808.33       $875.5557   $875.56   $875.55   $875.80