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	$207.87	6.736%	$221.8721	$221.87	$221.85	$221.90
Purchase #2	$149.36	13.484%	$169.4997	$169.50	$169.50	$169.50
Purchase #3	$145.83	4.558%	$152.4769	$152.48	$152.50	$152.50
Purchase #4	$165.88	4.115%	$172.706	$172.71	$172.70	$172.70
Purchase #5	$82.99	7.571%	$89.2732	$89.27	$89.25	$89.30
Purchase #6	$181.60	7.377%	$194.9966	$195.00	$195.00	$195.00
Purchase #7	$88.91	11.634%	$99.2538	$99.25	$99.25	$99.30
7 purchase totals =	$1,022.44		$1,100.0783	$1,100.08	$1,100.05	$1,100.20