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	$98.64	8.634%	$107.1566	$107.16	$107.15	$107.20
Purchase #2	$234.40	3.621%	$242.8876	$242.89	$242.90	$242.90
Purchase #3	$246.70	11.600%	$275.3172	$275.32	$275.30	$275.30
Purchase #4	$59.52	12.592%	$67.0148	$67.01	$67.00	$67.00
Purchase #5	$53.95	9.858%	$59.2684	$59.27	$59.25	$59.30
Purchase #6	$196.48	11.785%	$219.6352	$219.64	$219.65	$219.60
Purchase #7	$70.25	4.707%	$73.5567	$73.56	$73.55	$73.60
7 purchase totals =	$959.94		$1,044.8365	$1,044.85	$1,044.80	$1,044.90