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	$148.89	11.347%	$165.7845	$165.78	$165.80	$165.80
Purchase #2	$127.46	10.504%	$140.8484	$140.85	$140.85	$140.80
Purchase #3	$144.46	9.338%	$157.9497	$157.95	$157.95	$157.90
Purchase #4	$247.29	8.485%	$268.2726	$268.27	$268.25	$268.30
Purchase #5	$12.40	6.122%	$13.1591	$13.16	$13.15	$13.20
Purchase #6	$81.57	5.813%	$86.3117	$86.31	$86.30	$86.30
Purchase #7	$174.50	10.532%	$192.8783	$192.88	$192.90	$192.90
7 purchase totals =	$936.57		$1,025.2043	$1,025.20	$1,025.20	$1,025.20