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	$102.30	10.668%	$113.2134	$113.21	$113.20	$113.20
Purchase #2	$228.31	8.721%	$248.2209	$248.22	$248.20	$248.20
Purchase #3	$236.83	8.288%	$256.4585	$256.46	$256.45	$256.50
Purchase #4	$165.78	3.733%	$171.9686	$171.97	$171.95	$172.00
Purchase #5	$51.86	7.311%	$55.6515	$55.65	$55.65	$55.70
Purchase #6	$67.79	12.600%	$76.3315	$76.33	$76.35	$76.30
Purchase #7	$164.78	4.397%	$172.0254	$172.03	$172.05	$172.00
7 purchase totals =	$1,017.65		$1,093.8698	$1,093.87	$1,093.85	$1,093.90