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	$107.89	3.755%	$111.9413	$111.94	$111.95	$111.90
Purchase #2	$223.35	12.247%	$250.7037	$250.70	$250.70	$250.70
Purchase #3	$32.47	4.338%	$33.8785	$33.88	$33.90	$33.90
Purchase #4	$141.49	5.781%	$149.6695	$149.67	$149.65	$149.70
Purchase #5	$59.73	8.584%	$64.8572	$64.86	$64.85	$64.90
Purchase #6	$126.70	7.824%	$136.613	$136.61	$136.60	$136.60
Purchase #7	$127.82	8.864%	$139.15	$139.15	$139.15	$139.20
7 purchase totals =	$819.45		$886.8132	$886.81	$886.80	$886.90