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	$59.30	13.857%	$67.5172	$67.52	$67.50	$67.50
Purchase #2	$169.56	3.625%	$175.7066	$175.71	$175.70	$175.70
Purchase #3	$157.89	6.834%	$168.6802	$168.68	$168.70	$168.70
Purchase #4	$71.68	13.391%	$81.2787	$81.28	$81.30	$81.30
Purchase #5	$93.92	12.552%	$105.7088	$105.71	$105.70	$105.70
Purchase #6	$240.99	12.255%	$270.5233	$270.52	$270.50	$270.50
Purchase #7	$208.89	10.752%	$231.3499	$231.35	$231.35	$231.30
7 purchase totals =	$1,002.23		$1,100.7647	$1,100.77	$1,100.75	$1,100.70