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	$66.32	11.813%	$74.1544	$74.15	$74.15	$74.20
Purchase #2	$61.55	6.446%	$65.5175	$65.52	$65.50	$65.50
Purchase #3	$242.39	8.475%	$262.9326	$262.93	$262.95	$262.90
Purchase #4	$218.90	7.484%	$235.2825	$235.28	$235.30	$235.30
Purchase #5	$229.91	4.498%	$240.2514	$240.25	$240.25	$240.30
Purchase #6	$39.63	7.106%	$42.4461	$42.45	$42.45	$42.40
Purchase #7	$105.90	5.506%	$111.7309	$111.73	$111.75	$111.70
7 purchase totals =	$964.60		$1,032.3154	$1,032.31	$1,032.35	$1,032.30