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	$172.86	9.621%	$189.4909	$189.49	$189.50	$189.50
Purchase #2	$102.69	8.691%	$111.6148	$111.61	$111.60	$111.60
Purchase #3	$30.48	4.628%	$31.8906	$31.89	$31.90	$31.90
Purchase #4	$168.66	6.626%	$179.8354	$179.84	$179.85	$179.80
Purchase #5	$193.44	9.680%	$212.165	$212.17	$212.15	$212.20
Purchase #6	$31.55	6.422%	$33.5761	$33.58	$33.60	$33.60
Purchase #7	$174.69	10.767%	$193.4989	$193.50	$193.50	$193.50
7 purchase totals =	$874.37		$952.0717	$952.08	$952.10	$952.10