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	$215.25	12.361%	$241.8571	$241.86	$241.85	$241.90
Purchase #2	$28.92	13.275%	$32.7591	$32.76	$32.75	$32.80
Purchase #3	$60.68	5.693%	$64.1345	$64.13	$64.15	$64.10
Purchase #4	$112.72	4.417%	$117.6988	$117.70	$117.70	$117.70
Purchase #5	$141.28	13.116%	$159.8103	$159.81	$159.80	$159.80
Purchase #6	$89.88	6.130%	$95.3896	$95.39	$95.40	$95.40
Purchase #7	$208.75	6.698%	$222.7321	$222.73	$222.75	$222.70
7 purchase totals =	$857.48		$934.3815	$934.38	$934.40	$934.40