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	$101.34	12.165%	$113.668	$113.67	$113.65	$113.70
Purchase #2	$87.65	9.227%	$95.7375	$95.74	$95.75	$95.70
Purchase #3	$59.44	4.860%	$62.3288	$62.33	$62.35	$62.30
Purchase #4	$80.40	3.553%	$83.2566	$83.26	$83.25	$83.30
Purchase #5	$192.38	11.494%	$214.4922	$214.49	$214.50	$214.50
Purchase #6	$100.34	11.204%	$111.5821	$111.58	$111.60	$111.60
Purchase #7	$177.76	3.714%	$184.362	$184.36	$184.35	$184.40
7 purchase totals =	$799.31		$865.4272	$865.43	$865.45	$865.50