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	$250.61	7.512%	$269.4358	$269.44	$269.45	$269.40
Purchase #2	$60.29	6.444%	$64.1751	$64.18	$64.20	$64.20
Purchase #3	$169.84	8.652%	$184.5346	$184.53	$184.55	$184.50
Purchase #4	$60.46	3.690%	$62.691	$62.69	$62.70	$62.70
Purchase #5	$130.34	11.267%	$145.0254	$145.03	$145.05	$145.00
Purchase #6	$38.94	9.428%	$42.6113	$42.61	$42.60	$42.60
Purchase #7	$172.59	13.501%	$195.8914	$195.89	$195.90	$195.90
7 purchase totals =	$883.07		$964.3646	$964.37	$964.45	$964.30