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	$141.80	11.106%	$157.5483	$157.55	$157.55	$157.50
Purchase #2	$208.31	3.496%	$215.5925	$215.59	$215.60	$215.60
Purchase #3	$239.46	5.870%	$253.5163	$253.52	$253.50	$253.50
Purchase #4	$225.84	6.400%	$240.2938	$240.29	$240.30	$240.30
Purchase #5	$233.55	9.390%	$255.4803	$255.48	$255.50	$255.50
Purchase #6	$164.53	13.406%	$186.5869	$186.59	$186.60	$186.60
Purchase #7	$62.46	8.223%	$67.5961	$67.60	$67.60	$67.60
7 purchase totals =	$1,275.95		$1,376.6142	$1,376.62	$1,376.65	$1,376.60