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	$215.35	8.325%	$233.2779	$233.28	$233.30	$233.30
Purchase #2	$112.69	6.137%	$119.6058	$119.61	$119.60	$119.60
Purchase #3	$59.55	13.830%	$67.7858	$67.79	$67.80	$67.80
Purchase #4	$173.58	11.831%	$194.1162	$194.12	$194.10	$194.10
Purchase #5	$75.93	8.153%	$82.1206	$82.12	$82.10	$82.10
Purchase #6	$60.28	11.590%	$67.2665	$67.27	$67.25	$67.30
Purchase #7	$168.78	6.294%	$179.403	$179.40	$179.40	$179.40
7 purchase totals =	$866.16		$943.5758	$943.59	$943.55	$943.60