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	$144.26	11.356%	$160.6422	$160.64	$160.65	$160.60
Purchase #2	$70.69	4.103%	$73.5904	$73.59	$73.60	$73.60
Purchase #3	$132.32	6.732%	$141.2278	$141.23	$141.25	$141.20
Purchase #4	$49.43	5.580%	$52.1882	$52.19	$52.20	$52.20
Purchase #5	$73.44	8.368%	$79.5855	$79.59	$79.60	$79.60
Purchase #6	$123.41	7.208%	$132.3054	$132.31	$132.30	$132.30
Purchase #7	$104.62	6.742%	$111.6735	$111.67	$111.65	$111.70
7 purchase totals =	$698.17		$751.2130	$751.22	$751.25	$751.20