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	$33.52	13.219%	$37.951	$37.95	$37.95	$38.00
Purchase #2	$42.89	13.691%	$48.7621	$48.76	$48.75	$48.80
Purchase #3	$59.73	4.572%	$62.4609	$62.46	$62.45	$62.50
Purchase #4	$156.88	7.369%	$168.4405	$168.44	$168.45	$168.40
Purchase #5	$203.40	13.331%	$230.5153	$230.52	$230.50	$230.50
Purchase #6	$27.76	9.445%	$30.3819	$30.38	$30.40	$30.40
Purchase #7	$24.73	6.686%	$26.3834	$26.38	$26.40	$26.40
7 purchase totals =	$548.91		$604.8951	$604.89	$604.90	$605.00