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	$79.84	4.151%	$83.1542	$83.15	$83.15	$83.20
Purchase #2	$86.57	10.760%	$95.8849	$95.88	$95.90	$95.90
Purchase #3	$222.40	11.308%	$247.549	$247.55	$247.55	$247.50
Purchase #4	$210.57	5.753%	$222.6841	$222.68	$222.70	$222.70
Purchase #5	$218.76	5.466%	$230.7174	$230.72	$230.70	$230.70
Purchase #6	$64.47	3.761%	$66.8947	$66.89	$66.90	$66.90
Purchase #7	$90.96	4.322%	$94.8913	$94.89	$94.90	$94.90
7 purchase totals =	$973.57		$1,041.7756	$1,041.76	$1,041.80	$1,041.80