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	$209.35	7.511%	$225.0743	$225.07	$225.05	$225.10
Purchase #2	$38.34	13.866%	$43.6562	$43.66	$43.65	$43.70
Purchase #3	$80.99	8.672%	$88.0135	$88.01	$88.00	$88.00
Purchase #4	$55.29	7.628%	$59.5075	$59.51	$59.50	$59.50
Purchase #5	$121.73	4.630%	$127.3661	$127.37	$127.35	$127.40
Purchase #6	$15.73	11.644%	$17.5616	$17.56	$17.55	$17.60
Purchase #7	$247.98	9.319%	$271.0893	$271.09	$271.10	$271.10
7 purchase totals =	$769.41		$832.2685	$832.27	$832.20	$832.40