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 $88.96   9.783%   $97.663   $97.66   $97.65   $97.70  
  Purchase #2 $197.60   7.266%   $211.9576   $211.96   $211.95   $212.00  
  Purchase #3 $217.93   7.221%   $233.6667   $233.67   $233.65   $233.70  
  Purchase #4 $219.74   3.561%   $227.5649   $227.56   $227.55   $227.60  
  Purchase #5 $52.48   6.309%   $55.791   $55.79   $55.80   $55.80  
  Purchase #6 $79.74   9.267%   $87.1295   $87.13   $87.15   $87.10  
  Purchase #7 $238.68   3.432%   $246.8715   $246.87   $246.85   $246.90  
  7 purchase totals = $1,095.13       $1,160.6442   $1,160.64   $1,160.60   $1,160.80