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	$106.71	3.213%	$110.1386	$110.14	$110.15	$110.10
Purchase #2	$104.46	12.370%	$117.3817	$117.38	$117.40	$117.40
Purchase #3	$209.49	3.857%	$217.57	$217.57	$217.55	$217.60
Purchase #4	$229.54	13.812%	$261.2441	$261.24	$261.25	$261.20
Purchase #5	$29.76	12.138%	$33.3723	$33.37	$33.35	$33.40
Purchase #6	$88.42	13.844%	$100.6609	$100.66	$100.65	$100.70
Purchase #7	$156.52	10.287%	$172.6212	$172.62	$172.60	$172.60
7 purchase totals =	$924.90		$1,012.9888	$1,012.98	$1,012.95	$1,013.00