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	$45.37	7.352%	$48.7056	$48.71	$48.70	$48.70
Purchase #2	$177.62	4.501%	$185.6147	$185.61	$185.60	$185.60
Purchase #3	$41.51	9.655%	$45.5178	$45.52	$45.50	$45.50
Purchase #4	$197.56	12.344%	$221.9468	$221.95	$221.95	$221.90
Purchase #5	$173.73	10.438%	$191.8639	$191.86	$191.85	$191.90
Purchase #6	$235.27	12.414%	$264.4764	$264.48	$264.50	$264.50
Purchase #7	$128.66	5.693%	$135.9846	$135.98	$136.00	$136.00
7 purchase totals =	$999.72		$1,094.1098	$1,094.11	$1,094.10	$1,094.10