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	$174.97	4.181%	$182.2855	$182.29	$182.30	$182.30
Purchase #2	$81.79	6.764%	$87.3223	$87.32	$87.30	$87.30
Purchase #3	$29.49	13.362%	$33.4305	$33.43	$33.45	$33.40
Purchase #4	$188.35	11.698%	$210.3832	$210.38	$210.40	$210.40
Purchase #5	$76.99	7.304%	$82.6133	$82.61	$82.60	$82.60
Purchase #6	$16.96	10.300%	$18.7069	$18.71	$18.70	$18.70
Purchase #7	$89.90	6.444%	$95.6932	$95.69	$95.70	$95.70
7 purchase totals =	$658.45		$710.4349	$710.43	$710.45	$710.40