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	$200.64	6.218%	$213.1158	$213.12	$213.10	$213.10
Purchase #2	$37.77	7.200%	$40.4894	$40.49	$40.50	$40.50
Purchase #3	$167.97	6.511%	$178.9065	$178.91	$178.90	$178.90
Purchase #4	$246.98	12.812%	$278.6231	$278.62	$278.60	$278.60
Purchase #5	$78.88	13.246%	$89.3284	$89.33	$89.35	$89.30
Purchase #6	$214.97	5.726%	$227.2792	$227.28	$227.30	$227.30
Purchase #7	$16.76	10.149%	$18.461	$18.46	$18.45	$18.50
7 purchase totals =	$963.97		$1,046.2034	$1,046.21	$1,046.20	$1,046.20