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	$89.27	7.437%	$95.909	$95.91	$95.90	$95.90
Purchase #2	$134.25	13.842%	$152.8329	$152.83	$152.85	$152.80
Purchase #3	$169.29	6.234%	$179.8435	$179.84	$179.85	$179.80
Purchase #4	$44.77	7.462%	$48.1107	$48.11	$48.10	$48.10
Purchase #5	$107.72	4.490%	$112.5566	$112.56	$112.55	$112.60
Purchase #6	$83.36	3.230%	$86.0525	$86.05	$86.05	$86.10
Purchase #7	$38.58	7.575%	$41.5024	$41.50	$41.50	$41.50
7 purchase totals =	$667.24		$716.8076	$716.80	$716.80	$716.80