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	$162.68	9.753%	$178.5462	$178.55	$178.55	$178.50
Purchase #2	$78.89	13.412%	$89.4707	$89.47	$89.45	$89.50
Purchase #3	$64.74	8.703%	$70.3743	$70.37	$70.35	$70.40
Purchase #4	$222.72	11.534%	$248.4085	$248.41	$248.40	$248.40
Purchase #5	$114.56	11.239%	$127.4354	$127.44	$127.45	$127.40
Purchase #6	$231.26	8.316%	$250.4916	$250.49	$250.50	$250.50
Purchase #7	$176.74	9.378%	$193.3147	$193.31	$193.30	$193.30
7 purchase totals =	$1,051.59		$1,158.0414	$1,158.04	$1,158.00	$1,158.00