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	$238.59	6.397%	$253.8526	$253.85	$253.85	$253.90
Purchase #2	$92.47	7.361%	$99.2767	$99.28	$99.30	$99.30
Purchase #3	$120.51	7.820%	$129.9339	$129.93	$129.95	$129.90
Purchase #4	$31.86	11.791%	$35.6166	$35.62	$35.60	$35.60
Purchase #5	$32.75	3.411%	$33.8671	$33.87	$33.85	$33.90
Purchase #6	$197.45	7.561%	$212.3792	$212.38	$212.40	$212.40
Purchase #7	$119.90	6.111%	$127.2271	$127.23	$127.25	$127.20
7 purchase totals =	$833.53		$892.1532	$892.16	$892.20	$892.20