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	$222.27	6.372%	$236.433	$236.43	$236.45	$236.40
Purchase #2	$189.56	11.489%	$211.3385	$211.34	$211.35	$211.30
Purchase #3	$118.81	7.478%	$127.6946	$127.69	$127.70	$127.70
Purchase #4	$195.98	13.390%	$222.2217	$222.22	$222.20	$222.20
Purchase #5	$50.56	8.625%	$54.9208	$54.92	$54.90	$54.90
Purchase #6	$159.43	4.264%	$166.2281	$166.23	$166.25	$166.20
Purchase #7	$74.74	7.355%	$80.2371	$80.24	$80.25	$80.20
7 purchase totals =	$1,011.35		$1,099.0738	$1,099.07	$1,099.10	$1,098.90