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	$145.94	12.424%	$164.0716	$164.07	$164.05	$164.10
Purchase #2	$37.95	4.606%	$39.698	$39.70	$39.70	$39.70
Purchase #3	$100.73	10.760%	$111.5685	$111.57	$111.55	$111.60
Purchase #4	$99.92	9.247%	$109.1596	$109.16	$109.15	$109.20
Purchase #5	$18.33	9.401%	$20.0532	$20.05	$20.05	$20.10
Purchase #6	$34.69	8.192%	$37.5318	$37.53	$37.55	$37.50
Purchase #7	$244.34	7.392%	$262.4016	$262.40	$262.40	$262.40
7 purchase totals =	$681.90		$744.4843	$744.48	$744.45	$744.60