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	$213.84	9.201%	$233.5154	$233.52	$233.50	$233.50
Purchase #2	$31.66	12.655%	$35.6666	$35.67	$35.65	$35.70
Purchase #3	$80.99	13.309%	$91.769	$91.77	$91.75	$91.80
Purchase #4	$48.59	9.185%	$53.053	$53.05	$53.05	$53.10
Purchase #5	$41.69	8.761%	$45.3425	$45.34	$45.35	$45.30
Purchase #6	$176.82	4.719%	$185.1641	$185.16	$185.15	$185.20
Purchase #7	$16.43	13.173%	$18.5943	$18.59	$18.60	$18.60
7 purchase totals =	$610.02		$663.1049	$663.10	$663.05	$663.20