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	$83.67	5.688%	$88.4291	$88.43	$88.45	$88.40
Purchase #2	$146.31	9.539%	$160.2665	$160.27	$160.25	$160.30
Purchase #3	$35.89	3.480%	$37.139	$37.14	$37.15	$37.10
Purchase #4	$185.62	3.395%	$191.9218	$191.92	$191.90	$191.90
Purchase #5	$222.77	13.829%	$253.5769	$253.58	$253.60	$253.60
Purchase #6	$27.49	10.491%	$30.374	$30.37	$30.35	$30.40
Purchase #7	$170.91	6.673%	$182.3148	$182.31	$182.30	$182.30
7 purchase totals =	$872.66		$944.0221	$944.02	$944.00	$944.00