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	$174.71	11.754%	$195.2454	$195.25	$195.25	$195.20
Purchase #2	$204.39	9.440%	$223.6844	$223.68	$223.70	$223.70
Purchase #3	$105.82	3.562%	$109.5893	$109.59	$109.60	$109.60
Purchase #4	$113.66	11.668%	$126.9218	$126.92	$126.90	$126.90
Purchase #5	$190.60	8.199%	$206.2273	$206.23	$206.25	$206.20
Purchase #6	$234.67	9.300%	$256.4943	$256.49	$256.50	$256.50
Purchase #7	$170.98	11.455%	$190.5658	$190.57	$190.55	$190.60
7 purchase totals =	$1,194.83		$1,308.7283	$1,308.73	$1,308.75	$1,308.70