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	$165.34	6.249%	$175.6721	$175.67	$175.65	$175.70
Purchase #2	$195.73	10.624%	$216.5244	$216.52	$216.50	$216.50
Purchase #3	$108.99	4.861%	$114.288	$114.29	$114.30	$114.30
Purchase #4	$104.93	4.311%	$109.4535	$109.45	$109.45	$109.50
Purchase #5	$158.42	10.220%	$174.6105	$174.61	$174.60	$174.60
Purchase #6	$153.34	8.597%	$166.5226	$166.52	$166.50	$166.50
Purchase #7	$123.48	4.283%	$128.7686	$128.77	$128.75	$128.80
7 purchase totals =	$1,010.23		$1,085.8397	$1,085.83	$1,085.75	$1,085.90