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	$60.25	12.153%	$67.5722	$67.57	$67.55	$67.60
Purchase #2	$115.64	4.430%	$120.7629	$120.76	$120.75	$120.80
Purchase #3	$207.53	10.790%	$229.9225	$229.92	$229.90	$229.90
Purchase #4	$37.78	3.519%	$39.1095	$39.11	$39.10	$39.10
Purchase #5	$167.94	13.717%	$190.9763	$190.98	$191.00	$191.00
Purchase #6	$144.39	12.521%	$162.4691	$162.47	$162.45	$162.50
Purchase #7	$122.30	6.779%	$130.5907	$130.59	$130.60	$130.60
7 purchase totals =	$855.83		$941.4032	$941.40	$941.35	$941.50