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	$67.73	5.818%	$71.6705	$71.67	$71.65	$71.70
Purchase #2	$158.35	3.567%	$163.9983	$164.00	$164.00	$164.00
Purchase #3	$130.82	12.817%	$147.5872	$147.59	$147.60	$147.60
Purchase #4	$203.76	11.596%	$227.388	$227.39	$227.40	$227.40
Purchase #5	$93.78	7.172%	$100.5059	$100.51	$100.50	$100.50
Purchase #6	$66.99	11.205%	$74.4962	$74.50	$74.50	$74.50
Purchase #7	$98.30	13.560%	$111.6295	$111.63	$111.65	$111.60
7 purchase totals =	$819.73		$897.2756	$897.29	$897.30	$897.30