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	$170.36	5.200%	$179.2187	$179.22	$179.20	$179.20
Purchase #2	$37.84	6.580%	$40.3299	$40.33	$40.35	$40.30
Purchase #3	$88.68	13.441%	$100.5995	$100.60	$100.60	$100.60
Purchase #4	$250.96	3.411%	$259.5202	$259.52	$259.50	$259.50
Purchase #5	$85.61	8.375%	$92.7798	$92.78	$92.80	$92.80
Purchase #6	$81.44	7.389%	$87.4576	$87.46	$87.45	$87.50
Purchase #7	$240.38	5.651%	$253.9639	$253.96	$253.95	$254.00
7 purchase totals =	$955.27		$1,013.8696	$1,013.87	$1,013.85	$1,013.90