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	$145.50	13.620%	$165.3171	$165.32	$165.30	$165.30
Purchase #2	$164.95	11.276%	$183.5498	$183.55	$183.55	$183.50
Purchase #3	$65.55	3.482%	$67.8325	$67.83	$67.85	$67.80
Purchase #4	$239.43	8.371%	$259.4727	$259.47	$259.45	$259.50
Purchase #5	$148.64	12.277%	$166.8885	$166.89	$166.90	$166.90
Purchase #6	$87.75	13.681%	$99.7551	$99.76	$99.75	$99.80
Purchase #7	$117.88	3.815%	$122.3771	$122.38	$122.40	$122.40
7 purchase totals =	$969.70		$1,065.1928	$1,065.20	$1,065.20	$1,065.20