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 $224.55   4.732%   $235.1757   $235.18   $235.20   $235.20  
  Purchase #2 $44.49   11.508%   $49.6099   $49.61   $49.60   $49.60  
  Purchase #3 $101.49   6.508%   $108.095   $108.10   $108.10   $108.10  
  Purchase #4 $203.41   6.209%   $216.0397   $216.04   $216.05   $216.00  
  Purchase #5 $198.59   6.425%   $211.3494   $211.35   $211.35   $211.30  
  Purchase #6 $152.67   9.458%   $167.1095   $167.11   $167.10   $167.10  
  Purchase #7 $177.68   9.284%   $194.1758   $194.18   $194.20   $194.20  
  7 purchase totals = $1,102.88       $1,181.5550   $1,181.57   $1,181.60   $1,181.50