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	$225.76	8.243%	$244.3694	$244.37	$244.35	$244.40
Purchase #2	$69.67	4.303%	$72.6679	$72.67	$72.65	$72.70
Purchase #3	$69.49	3.361%	$71.8256	$71.83	$71.85	$71.80
Purchase #4	$222.72	3.184%	$229.8114	$229.81	$229.80	$229.80
Purchase #5	$147.53	6.115%	$156.5515	$156.55	$156.55	$156.60
Purchase #6	$95.82	4.835%	$100.4529	$100.45	$100.45	$100.50
Purchase #7	$30.64	4.344%	$31.971	$31.97	$31.95	$32.00
7 purchase totals =	$861.63		$907.6497	$907.65	$907.60	$907.80