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	$143.35	4.716%	$150.1104	$150.11	$150.10	$150.10
Purchase #2	$219.77	5.847%	$232.62	$232.62	$232.60	$232.60
Purchase #3	$89.90	8.585%	$97.6179	$97.62	$97.60	$97.60
Purchase #4	$79.72	11.717%	$89.0608	$89.06	$89.05	$89.10
Purchase #5	$172.26	4.333%	$179.724	$179.72	$179.70	$179.70
Purchase #6	$30.67	4.494%	$32.0483	$32.05	$32.05	$32.00
Purchase #7	$235.85	12.463%	$265.244	$265.24	$265.25	$265.20
7 purchase totals =	$971.52		$1,046.4254	$1,046.42	$1,046.35	$1,046.30