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	$118.65	13.635%	$134.8279	$134.83	$134.85	$134.80
Purchase #2	$152.66	12.770%	$172.1547	$172.15	$172.15	$172.20
Purchase #3	$199.98	4.566%	$209.1111	$209.11	$209.10	$209.10
Purchase #4	$32.28	11.447%	$35.9751	$35.98	$36.00	$36.00
Purchase #5	$8.72	11.172%	$9.6942	$9.69	$9.70	$9.70
Purchase #6	$214.60	4.188%	$223.5874	$223.59	$223.60	$223.60
Purchase #7	$238.25	11.244%	$265.0388	$265.04	$265.05	$265.00
7 purchase totals =	$965.14		$1,050.3892	$1,050.39	$1,050.45	$1,050.40