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	$67.46	7.477%	$72.504	$72.50	$72.50	$72.50
Purchase #2	$136.55	8.118%	$147.6351	$147.64	$147.65	$147.60
Purchase #3	$155.55	13.462%	$176.4901	$176.49	$176.50	$176.50
Purchase #4	$218.65	7.668%	$235.4161	$235.42	$235.40	$235.40
Purchase #5	$49.99	11.803%	$55.8903	$55.89	$55.90	$55.90
Purchase #6	$140.88	12.794%	$158.9042	$158.90	$158.90	$158.90
Purchase #7	$199.37	7.626%	$214.574	$214.57	$214.55	$214.60
7 purchase totals =	$968.45		$1,061.4138	$1,061.41	$1,061.40	$1,061.40