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	$244.39	9.313%	$267.15	$267.15	$267.15	$267.20
Purchase #2	$101.79	11.843%	$113.845	$113.85	$113.85	$113.80
Purchase #3	$74.59	5.829%	$78.9379	$78.94	$78.95	$78.90
Purchase #4	$55.90	10.444%	$61.7382	$61.74	$61.75	$61.70
Purchase #5	$161.97	3.135%	$167.0478	$167.05	$167.05	$167.00
Purchase #6	$120.68	13.345%	$136.7847	$136.78	$136.80	$136.80
Purchase #7	$67.57	7.535%	$72.6614	$72.66	$72.65	$72.70
7 purchase totals =	$826.89		$898.1650	$898.17	$898.20	$898.10