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 $142.56   9.657%   $156.327   $156.33   $156.35   $156.30  
  Purchase #2 $197.59   4.215%   $205.9184   $205.92   $205.90   $205.90  
  Purchase #3 $211.71   6.855%   $226.2227   $226.22   $226.20   $226.20  
  Purchase #4 $111.84   9.600%   $122.5766   $122.58   $122.60   $122.60  
  Purchase #5 $212.81   7.174%   $228.077   $228.08   $228.10   $228.10  
  Purchase #6 $56.93   10.319%   $62.8046   $62.80   $62.80   $62.80  
  Purchase #7 $90.53   13.343%   $102.6094   $102.61   $102.60   $102.60  
  7 purchase totals = $1,023.97       $1,104.5357   $1,104.54   $1,104.55   $1,104.50