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	$115.71	4.283%	$120.6659	$120.67	$120.65	$120.70
Purchase #2	$25.55	5.228%	$26.8858	$26.89	$26.90	$26.90
Purchase #3	$164.59	12.554%	$185.2526	$185.25	$185.25	$185.30
Purchase #4	$141.53	6.500%	$150.7295	$150.73	$150.75	$150.70
Purchase #5	$246.87	4.344%	$257.594	$257.59	$257.60	$257.60
Purchase #6	$157.48	6.318%	$167.4296	$167.43	$167.45	$167.40
Purchase #7	$231.42	13.871%	$263.5203	$263.52	$263.50	$263.50
7 purchase totals =	$1,083.15		$1,172.0777	$1,172.08	$1,172.10	$1,172.10