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	$82.35	7.134%	$88.2248	$88.22	$88.20	$88.20
Purchase #2	$45.61	5.589%	$48.1591	$48.16	$48.15	$48.20
Purchase #3	$250.40	10.368%	$276.3615	$276.36	$276.35	$276.40
Purchase #4	$55.65	8.394%	$60.3213	$60.32	$60.30	$60.30
Purchase #5	$114.61	11.308%	$127.5701	$127.57	$127.55	$127.60
Purchase #6	$65.82	9.826%	$72.2875	$72.29	$72.30	$72.30
Purchase #7	$113.90	10.506%	$125.8663	$125.87	$125.85	$125.90
7 purchase totals =	$728.34		$798.7906	$798.79	$798.70	$798.90