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	$158.29	13.357%	$179.4328	$179.43	$179.45	$179.40
Purchase #2	$28.51	9.859%	$31.3208	$31.32	$31.30	$31.30
Purchase #3	$245.45	12.358%	$275.7827	$275.78	$275.80	$275.80
Purchase #4	$84.58	11.554%	$94.3524	$94.35	$94.35	$94.40
Purchase #5	$221.61	7.465%	$238.1532	$238.15	$238.15	$238.20
Purchase #6	$48.48	12.675%	$54.6248	$54.62	$54.60	$54.60
Purchase #7	$198.67	6.110%	$210.8087	$210.81	$210.80	$210.80
7 purchase totals =	$985.59		$1,084.4754	$1,084.46	$1,084.45	$1,084.50