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	$33.35	11.304%	$37.1199	$37.12	$37.10	$37.10
Purchase #2	$8.64	3.116%	$8.9092	$8.91	$8.90	$8.90
Purchase #3	$15.78	3.377%	$16.3129	$16.31	$16.30	$16.30
Purchase #4	$65.95	6.843%	$70.463	$70.46	$70.45	$70.50
Purchase #5	$72.58	13.582%	$82.4378	$82.44	$82.45	$82.40
Purchase #6	$28.77	12.232%	$32.2891	$32.29	$32.30	$32.30
Purchase #7	$220.78	4.511%	$230.7394	$230.74	$230.75	$230.70
7 purchase totals =	$445.85		$478.2713	$478.27	$478.25	$478.20