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	$150.63	7.648%	$162.1502	$162.15	$162.15	$162.20
Purchase #2	$35.42	6.507%	$37.7248	$37.72	$37.70	$37.70
Purchase #3	$126.50	6.503%	$134.7263	$134.73	$134.75	$134.70
Purchase #4	$92.74	11.826%	$103.7074	$103.71	$103.70	$103.70
Purchase #5	$127.40	9.409%	$139.3871	$139.39	$139.40	$139.40
Purchase #6	$87.86	13.236%	$99.4891	$99.49	$99.50	$99.50
Purchase #7	$211.52	4.561%	$221.1674	$221.17	$221.15	$221.20
7 purchase totals =	$832.07		$898.3523	$898.36	$898.35	$898.40