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	$198.30	5.144%	$208.5006	$208.50	$208.50	$208.50
Purchase #2	$181.67	10.639%	$200.9979	$201.00	$201.00	$201.00
Purchase #3	$63.84	6.233%	$67.8191	$67.82	$67.80	$67.80
Purchase #4	$165.39	8.272%	$179.0711	$179.07	$179.05	$179.10
Purchase #5	$169.92	7.643%	$182.907	$182.91	$182.90	$182.90
Purchase #6	$146.38	12.832%	$165.1635	$165.16	$165.15	$165.20
Purchase #7	$89.31	12.832%	$100.7703	$100.77	$100.75	$100.80
7 purchase totals =	$1,014.81		$1,105.2295	$1,105.23	$1,105.15	$1,105.30