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	$122.96	8.734%	$133.6993	$133.70	$133.70	$133.70
Purchase #2	$74.48	5.780%	$78.7849	$78.78	$78.80	$78.80
Purchase #3	$98.68	6.611%	$105.2037	$105.20	$105.20	$105.20
Purchase #4	$139.55	10.145%	$153.7073	$153.71	$153.70	$153.70
Purchase #5	$90.93	11.585%	$101.4642	$101.46	$101.45	$101.50
Purchase #6	$103.94	7.202%	$111.4258	$111.43	$111.45	$111.40
Purchase #7	$154.70	6.743%	$165.1314	$165.13	$165.15	$165.10
7 purchase totals =	$785.24		$849.4166	$849.41	$849.45	$849.40