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	$48.55	12.749%	$54.7396	$54.74	$54.75	$54.70
Purchase #2	$205.95	6.778%	$219.9093	$219.91	$219.90	$219.90
Purchase #3	$81.52	11.375%	$90.7929	$90.79	$90.80	$90.80
Purchase #4	$247.71	12.872%	$279.5952	$279.60	$279.60	$279.60
Purchase #5	$244.96	11.752%	$273.7477	$273.75	$273.75	$273.70
Purchase #6	$9.44	13.579%	$10.7219	$10.72	$10.70	$10.70
Purchase #7	$125.42	13.375%	$142.1949	$142.19	$142.20	$142.20
7 purchase totals =	$963.55		$1,071.7015	$1,071.70	$1,071.70	$1,071.60