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	$88.89	5.739%	$93.9914	$93.99	$94.00	$94.00
Purchase #2	$28.80	13.484%	$32.6834	$32.68	$32.70	$32.70
Purchase #3	$57.43	3.287%	$59.3177	$59.32	$59.30	$59.30
Purchase #4	$71.78	12.820%	$80.9822	$80.98	$81.00	$81.00
Purchase #5	$90.27	10.197%	$99.4748	$99.47	$99.45	$99.50
Purchase #6	$165.41	11.841%	$184.9962	$185.00	$185.00	$185.00
Purchase #7	$67.45	5.337%	$71.0498	$71.05	$71.05	$71.00
7 purchase totals =	$570.03		$622.4955	$622.49	$622.50	$622.50