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	$29.58	10.607%	$32.7176	$32.72	$32.70	$32.70
Purchase #2	$145.33	10.434%	$160.4937	$160.49	$160.50	$160.50
Purchase #3	$50.82	3.239%	$52.4661	$52.47	$52.45	$52.50
Purchase #4	$102.84	10.234%	$113.3646	$113.36	$113.35	$113.40
Purchase #5	$35.89	13.443%	$40.7147	$40.71	$40.70	$40.70
Purchase #6	$158.63	10.814%	$175.7842	$175.78	$175.80	$175.80
Purchase #7	$117.81	7.472%	$126.6128	$126.61	$126.60	$126.60
7 purchase totals =	$640.90		$702.1537	$702.14	$702.10	$702.20