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	$147.55	5.667%	$155.9117	$155.91	$155.90	$155.90
Purchase #2	$55.37	11.776%	$61.8904	$61.89	$61.90	$61.90
Purchase #3	$150.39	12.266%	$168.8368	$168.84	$168.85	$168.80
Purchase #4	$17.37	11.561%	$19.3781	$19.38	$19.40	$19.40
Purchase #5	$46.72	8.704%	$50.7865	$50.79	$50.80	$50.80
Purchase #6	$239.31	6.469%	$254.791	$254.79	$254.80	$254.80
Purchase #7	$142.31	10.324%	$157.0021	$157.00	$157.00	$157.00
7 purchase totals =	$799.02		$868.5966	$868.60	$868.65	$868.60