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	$152.60	8.698%	$165.8731	$165.87	$165.85	$165.90
Purchase #2	$198.38	12.804%	$223.7806	$223.78	$223.80	$223.80
Purchase #3	$92.65	13.694%	$105.3375	$105.34	$105.35	$105.30
Purchase #4	$182.38	4.520%	$190.6236	$190.62	$190.60	$190.60
Purchase #5	$189.60	8.421%	$205.5662	$205.57	$205.55	$205.60
Purchase #6	$6.94	12.476%	$7.8058	$7.81	$7.80	$7.80
Purchase #7	$223.55	4.800%	$234.2804	$234.28	$234.30	$234.30
7 purchase totals =	$1,046.10		$1,133.2672	$1,133.27	$1,133.25	$1,133.30