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	$153.90	7.588%	$165.5779	$165.58	$165.60	$165.60
Purchase #2	$223.88	13.417%	$253.918	$253.92	$253.90	$253.90
Purchase #3	$179.49	3.199%	$185.2319	$185.23	$185.25	$185.20
Purchase #4	$188.71	10.862%	$209.2077	$209.21	$209.20	$209.20
Purchase #5	$94.78	12.779%	$106.8919	$106.89	$106.90	$106.90
Purchase #6	$99.81	8.831%	$108.6242	$108.62	$108.60	$108.60
Purchase #7	$128.79	13.259%	$145.8663	$145.87	$145.85	$145.90
7 purchase totals =	$1,069.36		$1,175.3179	$1,175.32	$1,175.30	$1,175.30