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	$233.41	9.589%	$255.7917	$255.79	$255.80	$255.80
Purchase #2	$89.38	12.448%	$100.506	$100.51	$100.50	$100.50
Purchase #3	$210.40	10.773%	$233.0664	$233.07	$233.05	$233.10
Purchase #4	$83.29	6.687%	$88.8596	$88.86	$88.85	$88.90
Purchase #5	$179.71	11.786%	$200.8906	$200.89	$200.90	$200.90
Purchase #6	$119.97	4.418%	$125.2703	$125.27	$125.25	$125.30
Purchase #7	$243.27	5.263%	$256.0733	$256.07	$256.05	$256.10
7 purchase totals =	$1,159.43		$1,260.4579	$1,260.46	$1,260.40	$1,260.60