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	$96.50	8.456%	$104.66	$104.66	$104.65	$104.70
Purchase #2	$72.64	4.778%	$76.1107	$76.11	$76.10	$76.10
Purchase #3	$184.31	4.300%	$192.2353	$192.24	$192.25	$192.20
Purchase #4	$55.58	7.231%	$59.599	$59.60	$59.60	$59.60
Purchase #5	$242.40	6.622%	$258.4517	$258.45	$258.45	$258.50
Purchase #6	$179.75	8.634%	$195.2696	$195.27	$195.25	$195.30
Purchase #7	$75.60	12.593%	$85.1203	$85.12	$85.10	$85.10
7 purchase totals =	$906.78		$971.4466	$971.45	$971.40	$971.50