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 $58.29   7.337%   $62.5667   $62.57   $62.55   $62.60  
  Purchase #2 $149.99   11.247%   $166.8594   $166.86   $166.85   $166.90  
  Purchase #3 $204.32   9.196%   $223.1093   $223.11   $223.10   $223.10  
  Purchase #4 $118.98   4.562%   $124.4079   $124.41   $124.40   $124.40  
  Purchase #5 $106.28   8.690%   $115.5157   $115.52   $115.50   $115.50  
  Purchase #6 $123.32   12.672%   $138.9471   $138.95   $138.95   $138.90  
  Purchase #7 $157.72   10.799%   $174.7522   $174.75   $174.75   $174.80  
  7 purchase totals = $918.90       $1,006.1583   $1,006.17   $1,006.10   $1,006.20