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	$218.64	10.464%	$241.5185	$241.52	$241.50	$241.50
Purchase #2	$24.78	11.260%	$27.5702	$27.57	$27.55	$27.60
Purchase #3	$100.59	8.700%	$109.3413	$109.34	$109.35	$109.30
Purchase #4	$188.32	10.843%	$208.7395	$208.74	$208.75	$208.70
Purchase #5	$30.97	9.406%	$33.883	$33.88	$33.90	$33.90
Purchase #6	$231.93	11.120%	$257.7206	$257.72	$257.70	$257.70
Purchase #7	$146.39	12.678%	$164.9493	$164.95	$164.95	$164.90
7 purchase totals =	$941.62		$1,043.7224	$1,043.72	$1,043.70	$1,043.60