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	$88.93	7.623%	$95.7091	$95.71	$95.70	$95.70
Purchase #2	$89.43	11.175%	$99.4238	$99.42	$99.40	$99.40
Purchase #3	$136.76	10.690%	$151.3796	$151.38	$151.40	$151.40
Purchase #4	$225.56	8.246%	$244.1597	$244.16	$244.15	$244.20
Purchase #5	$219.33	10.384%	$242.1052	$242.11	$242.10	$242.10
Purchase #6	$171.34	11.861%	$191.6626	$191.66	$191.65	$191.70
Purchase #7	$155.47	11.758%	$173.7502	$173.75	$173.75	$173.80
7 purchase totals =	$1,086.82		$1,198.1902	$1,198.19	$1,198.15	$1,198.30