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 $23.33   13.739%   $26.5353   $26.54   $26.55   $26.50  
  Purchase #2 $203.25   8.139%   $219.7925   $219.79   $219.80   $219.80  
  Purchase #3 $160.68   8.650%   $174.5788   $174.58   $174.60   $174.60  
  Purchase #4 $228.98   11.543%   $255.4112   $255.41   $255.40   $255.40  
  Purchase #5 $28.43   10.211%   $31.333   $31.33   $31.35   $31.30  
  Purchase #6 $213.79   11.437%   $238.2412   $238.24   $238.25   $238.20  
  Purchase #7 $136.57   9.239%   $149.1877   $149.19   $149.20   $149.20  
  7 purchase totals = $995.03       $1,095.0797   $1,095.08   $1,095.15   $1,095.00