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	$236.86	6.472%	$252.1896	$252.19	$252.20	$252.20
Purchase #2	$65.29	11.502%	$72.7997	$72.80	$72.80	$72.80
Purchase #3	$235.44	8.644%	$255.7914	$255.79	$255.80	$255.80
Purchase #4	$200.40	11.113%	$222.6705	$222.67	$222.65	$222.70
Purchase #5	$68.34	3.611%	$70.8078	$70.81	$70.80	$70.80
Purchase #6	$89.42	11.735%	$99.9134	$99.91	$99.90	$99.90
Purchase #7	$190.81	3.249%	$197.0094	$197.01	$197.00	$197.00
7 purchase totals =	$1,086.56		$1,171.1818	$1,171.18	$1,171.15	$1,171.20