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	$57.77	11.682%	$64.5187	$64.52	$64.50	$64.50
Purchase #2	$146.32	5.734%	$154.71	$154.71	$154.70	$154.70
Purchase #3	$204.61	9.697%	$224.451	$224.45	$224.45	$224.50
Purchase #4	$217.62	7.454%	$233.8414	$233.84	$233.85	$233.80
Purchase #5	$153.64	4.576%	$160.6706	$160.67	$160.65	$160.70
Purchase #6	$81.59	9.734%	$89.532	$89.53	$89.55	$89.50
Purchase #7	$79.50	10.338%	$87.7187	$87.72	$87.70	$87.70
7 purchase totals =	$941.05		$1,015.4424	$1,015.44	$1,015.40	$1,015.40