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	$184.34	6.417%	$196.1691	$196.17	$196.15	$196.20
Purchase #2	$195.55	5.804%	$206.8997	$206.90	$206.90	$206.90
Purchase #3	$224.49	12.108%	$251.6712	$251.67	$251.65	$251.70
Purchase #4	$56.31	8.754%	$61.2394	$61.24	$61.25	$61.20
Purchase #5	$87.89	3.692%	$91.1349	$91.13	$91.15	$91.10
Purchase #6	$83.33	7.590%	$89.6547	$89.65	$89.65	$89.70
Purchase #7	$242.27	8.186%	$262.1022	$262.10	$262.10	$262.10
7 purchase totals =	$1,074.18		$1,158.8712	$1,158.86	$1,158.85	$1,158.90