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	$250.83	3.724%	$260.1709	$260.17	$260.15	$260.20
Purchase #2	$154.41	3.156%	$159.2832	$159.28	$159.30	$159.30
Purchase #3	$239.45	10.283%	$264.0726	$264.07	$264.05	$264.10
Purchase #4	$224.56	7.102%	$240.5083	$240.51	$240.50	$240.50
Purchase #5	$34.31	6.747%	$36.6249	$36.62	$36.60	$36.60
Purchase #6	$91.81	3.359%	$94.8939	$94.89	$94.90	$94.90
Purchase #7	$40.67	5.508%	$42.9101	$42.91	$42.90	$42.90
7 purchase totals =	$1,036.04		$1,098.4639	$1,098.45	$1,098.40	$1,098.50