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	$85.80	11.276%	$95.4748	$95.47	$95.45	$95.50
Purchase #2	$35.56	11.333%	$39.59	$39.59	$39.60	$39.60
Purchase #3	$153.61	4.475%	$160.484	$160.48	$160.50	$160.50
Purchase #4	$11.92	3.250%	$12.3074	$12.31	$12.30	$12.30
Purchase #5	$46.71	8.274%	$50.5748	$50.57	$50.55	$50.60
Purchase #6	$232.47	8.846%	$253.0343	$253.03	$253.05	$253.00
Purchase #7	$71.49	7.735%	$77.0198	$77.02	$77.00	$77.00
7 purchase totals =	$637.56		$688.4851	$688.47	$688.45	$688.50