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	$193.33	11.743%	$216.0327	$216.03	$216.05	$216.00
Purchase #2	$119.41	13.438%	$135.4563	$135.46	$135.45	$135.50
Purchase #3	$77.87	6.399%	$82.8529	$82.85	$82.85	$82.90
Purchase #4	$126.43	5.773%	$133.7288	$133.73	$133.75	$133.70
Purchase #5	$146.59	4.777%	$153.5926	$153.59	$153.60	$153.60
Purchase #6	$148.70	11.503%	$165.805	$165.81	$165.80	$165.80
Purchase #7	$99.31	13.792%	$113.0068	$113.01	$113.00	$113.00
7 purchase totals =	$911.64		$1,000.4751	$1,000.48	$1,000.50	$1,000.50