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	$208.45	13.857%	$237.3349	$237.33	$237.35	$237.30
Purchase #2	$232.88	10.375%	$257.0413	$257.04	$257.05	$257.00
Purchase #3	$99.39	6.569%	$105.9189	$105.92	$105.90	$105.90
Purchase #4	$77.47	4.175%	$80.7044	$80.70	$80.70	$80.70
Purchase #5	$80.59	5.862%	$85.3142	$85.31	$85.30	$85.30
Purchase #6	$223.83	8.383%	$242.5937	$242.59	$242.60	$242.60
Purchase #7	$33.60	11.335%	$37.4086	$37.41	$37.40	$37.40
7 purchase totals =	$956.21		$1,046.3160	$1,046.30	$1,046.30	$1,046.20