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	$40.65	10.708%	$45.0028	$45.00	$45.00	$45.00
Purchase #2	$92.48	7.632%	$99.5381	$99.54	$99.55	$99.50
Purchase #3	$108.59	4.175%	$113.1236	$113.12	$113.10	$113.10
Purchase #4	$200.50	10.418%	$221.3881	$221.39	$221.40	$221.40
Purchase #5	$54.74	13.535%	$62.1491	$62.15	$62.15	$62.10
Purchase #6	$222.77	12.422%	$250.4425	$250.44	$250.45	$250.40
Purchase #7	$107.73	6.486%	$114.7174	$114.72	$114.70	$114.70
7 purchase totals =	$827.46		$906.3616	$906.36	$906.35	$906.20