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	$146.85	12.568%	$165.3061	$165.31	$165.30	$165.30
Purchase #2	$245.38	7.255%	$263.1823	$263.18	$263.20	$263.20
Purchase #3	$105.95	3.333%	$109.4813	$109.48	$109.50	$109.50
Purchase #4	$177.84	7.153%	$190.5609	$190.56	$190.55	$190.60
Purchase #5	$161.49	4.279%	$168.4002	$168.40	$168.40	$168.40
Purchase #6	$9.57	11.273%	$10.6488	$10.65	$10.65	$10.60
Purchase #7	$175.84	5.600%	$185.687	$185.69	$185.70	$185.70
7 purchase totals =	$1,022.92		$1,093.2666	$1,093.27	$1,093.30	$1,093.30