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	$240.27	5.139%	$252.6175	$252.62	$252.60	$252.60
Purchase #2	$164.47	10.831%	$182.2837	$182.28	$182.30	$182.30
Purchase #3	$119.81	3.586%	$124.1064	$124.11	$124.10	$124.10
Purchase #4	$179.29	11.836%	$200.5108	$200.51	$200.50	$200.50
Purchase #5	$240.25	6.382%	$255.5828	$255.58	$255.60	$255.60
Purchase #6	$80.78	9.500%	$88.4541	$88.45	$88.45	$88.50
Purchase #7	$51.67	13.452%	$58.6206	$58.62	$58.60	$58.60
7 purchase totals =	$1,076.54		$1,162.1759	$1,162.17	$1,162.15	$1,162.20