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	$216.56	10.393%	$239.0671	$239.07	$239.05	$239.10
Purchase #2	$225.72	11.610%	$251.9261	$251.93	$251.95	$251.90
Purchase #3	$245.59	10.279%	$270.8342	$270.83	$270.85	$270.80
Purchase #4	$45.88	13.709%	$52.1697	$52.17	$52.15	$52.20
Purchase #5	$85.94	3.832%	$89.2332	$89.23	$89.25	$89.20
Purchase #6	$117.30	4.287%	$122.3287	$122.33	$122.35	$122.30
Purchase #7	$27.59	3.529%	$28.5637	$28.56	$28.55	$28.60
7 purchase totals =	$964.58		$1,054.1227	$1,054.12	$1,054.15	$1,054.10