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	$221.82	7.475%	$238.401	$238.40	$238.40	$238.40
Purchase #2	$81.51	5.154%	$85.711	$85.71	$85.70	$85.70
Purchase #3	$10.72	3.551%	$11.1007	$11.10	$11.10	$11.10
Purchase #4	$146.61	12.452%	$164.8659	$164.87	$164.85	$164.90
Purchase #5	$58.36	13.304%	$66.1242	$66.12	$66.10	$66.10
Purchase #6	$109.42	10.223%	$120.606	$120.61	$120.60	$120.60
Purchase #7	$221.31	10.522%	$244.5962	$244.60	$244.60	$244.60
7 purchase totals =	$849.75		$931.4050	$931.41	$931.35	$931.40