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	$188.84	13.760%	$214.8244	$214.82	$214.80	$214.80
Purchase #2	$152.63	11.834%	$170.6922	$170.69	$170.70	$170.70
Purchase #3	$37.53	8.601%	$40.758	$40.76	$40.75	$40.80
Purchase #4	$58.65	4.512%	$61.2963	$61.30	$61.30	$61.30
Purchase #5	$62.90	4.510%	$65.7368	$65.74	$65.75	$65.70
Purchase #6	$185.39	13.279%	$210.0079	$210.01	$210.00	$210.00
Purchase #7	$99.69	5.322%	$104.9955	$105.00	$105.00	$105.00
7 purchase totals =	$785.63		$868.3111	$868.32	$868.30	$868.30