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	$195.37	13.427%	$221.6023	$221.60	$221.60	$221.60
Purchase #2	$39.38	11.388%	$43.8646	$43.86	$43.85	$43.90
Purchase #3	$232.64	5.702%	$245.9051	$245.91	$245.90	$245.90
Purchase #4	$71.92	10.572%	$79.5234	$79.52	$79.50	$79.50
Purchase #5	$127.71	7.835%	$137.7161	$137.72	$137.70	$137.70
Purchase #6	$161.25	12.760%	$181.8255	$181.83	$181.85	$181.80
Purchase #7	$33.47	13.808%	$38.0915	$38.09	$38.10	$38.10
7 purchase totals =	$861.74		$948.5285	$948.53	$948.50	$948.50