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	$249.43	5.145%	$262.2632	$262.26	$262.25	$262.30
Purchase #2	$55.31	6.756%	$59.0467	$59.05	$59.05	$59.00
Purchase #3	$201.74	11.763%	$225.4707	$225.47	$225.45	$225.50
Purchase #4	$82.60	6.619%	$88.0673	$88.07	$88.05	$88.10
Purchase #5	$70.70	11.354%	$78.7273	$78.73	$78.75	$78.70
Purchase #6	$235.25	12.373%	$264.3575	$264.36	$264.35	$264.40
Purchase #7	$40.85	11.824%	$45.6801	$45.68	$45.70	$45.70
7 purchase totals =	$935.88		$1,023.6128	$1,023.62	$1,023.60	$1,023.70