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	$135.75	11.111%	$150.8332	$150.83	$150.85	$150.80
Purchase #2	$56.44	9.449%	$61.773	$61.77	$61.75	$61.80
Purchase #3	$41.88	9.369%	$45.8037	$45.80	$45.80	$45.80
Purchase #4	$220.26	8.270%	$238.4755	$238.48	$238.50	$238.50
Purchase #5	$224.91	4.468%	$234.959	$234.96	$234.95	$235.00
Purchase #6	$225.97	13.281%	$255.9811	$255.98	$256.00	$256.00
Purchase #7	$230.67	10.801%	$255.5847	$255.58	$255.60	$255.60
7 purchase totals =	$1,135.88		$1,243.4102	$1,243.40	$1,243.45	$1,243.50