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	$227.50	8.692%	$247.2743	$247.27	$247.25	$247.30
Purchase #2	$87.50	4.141%	$91.1234	$91.12	$91.10	$91.10
Purchase #3	$209.48	6.219%	$222.5076	$222.51	$222.50	$222.50
Purchase #4	$44.92	4.269%	$46.8376	$46.84	$46.85	$46.80
Purchase #5	$157.53	9.141%	$171.9298	$171.93	$171.95	$171.90
Purchase #6	$169.69	9.290%	$185.4542	$185.45	$185.45	$185.50
Purchase #7	$10.53	7.283%	$11.2969	$11.30	$11.30	$11.30
7 purchase totals =	$907.15		$976.4238	$976.42	$976.40	$976.40