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	$219.73	7.737%	$236.7305	$236.73	$236.75	$236.70
Purchase #2	$185.33	6.118%	$196.6685	$196.67	$196.65	$196.70
Purchase #3	$189.71	7.434%	$203.813	$203.81	$203.80	$203.80
Purchase #4	$134.87	3.309%	$139.3328	$139.33	$139.35	$139.30
Purchase #5	$222.55	10.159%	$245.1589	$245.16	$245.15	$245.20
Purchase #6	$79.60	7.321%	$85.4275	$85.43	$85.45	$85.40
Purchase #7	$133.43	11.548%	$148.8385	$148.84	$148.85	$148.80
7 purchase totals =	$1,165.22		$1,255.9697	$1,255.97	$1,256.00	$1,255.90