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	$167.27	3.142%	$172.5256	$172.53	$172.55	$172.50
Purchase #2	$188.82	11.192%	$209.9527	$209.95	$209.95	$210.00
Purchase #3	$172.86	13.690%	$196.5245	$196.52	$196.50	$196.50
Purchase #4	$26.28	9.179%	$28.6922	$28.69	$28.70	$28.70
Purchase #5	$223.79	8.795%	$243.4723	$243.47	$243.45	$243.50
Purchase #6	$86.69	8.825%	$94.3404	$94.34	$94.35	$94.30
Purchase #7	$111.73	3.486%	$115.6249	$115.62	$115.60	$115.60
7 purchase totals =	$977.44		$1,061.1326	$1,061.12	$1,061.10	$1,061.10