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	$83.82	6.719%	$89.4519	$89.45	$89.45	$89.50
Purchase #2	$30.58	6.544%	$32.5812	$32.58	$32.60	$32.60
Purchase #3	$127.54	3.114%	$131.5116	$131.51	$131.50	$131.50
Purchase #4	$206.50	4.810%	$216.4327	$216.43	$216.45	$216.40
Purchase #5	$182.86	3.571%	$189.3899	$189.39	$189.40	$189.40
Purchase #6	$12.29	7.766%	$13.2444	$13.24	$13.25	$13.20
Purchase #7	$37.89	11.396%	$42.2079	$42.21	$42.20	$42.20
7 purchase totals =	$681.48		$714.8196	$714.81	$714.85	$714.80