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	$71.29	4.442%	$74.4567	$74.46	$74.45	$74.50
Purchase #2	$81.95	11.335%	$91.239	$91.24	$91.25	$91.20
Purchase #3	$237.84	5.480%	$250.8736	$250.87	$250.85	$250.90
Purchase #4	$47.25	7.432%	$50.7616	$50.76	$50.75	$50.80
Purchase #5	$85.52	13.668%	$97.2089	$97.21	$97.20	$97.20
Purchase #6	$248.96	10.512%	$275.1307	$275.13	$275.15	$275.10
Purchase #7	$238.85	9.215%	$260.86	$260.86	$260.85	$260.90
7 purchase totals =	$1,011.66		$1,100.5305	$1,100.53	$1,100.50	$1,100.60