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	$65.75	11.496%	$73.3086	$73.31	$73.30	$73.30
Purchase #2	$7.37	6.864%	$7.8759	$7.88	$7.90	$7.90
Purchase #3	$225.59	8.349%	$244.4245	$244.42	$244.40	$244.40
Purchase #4	$119.54	4.257%	$124.6288	$124.63	$124.65	$124.60
Purchase #5	$174.59	4.762%	$182.904	$182.90	$182.90	$182.90
Purchase #6	$208.48	7.309%	$223.7178	$223.72	$223.70	$223.70
Purchase #7	$132.35	13.554%	$150.2887	$150.29	$150.30	$150.30
7 purchase totals =	$933.67		$1,007.1483	$1,007.15	$1,007.15	$1,007.10