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	$192.43	9.386%	$210.4915	$210.49	$210.50	$210.50
Purchase #2	$231.31	10.601%	$255.8312	$255.83	$255.85	$255.80
Purchase #3	$60.86	8.181%	$65.839	$65.84	$65.85	$65.80
Purchase #4	$216.57	3.756%	$224.7044	$224.70	$224.70	$224.70
Purchase #5	$153.28	9.754%	$168.2309	$168.23	$168.25	$168.20
Purchase #6	$224.83	9.247%	$245.62	$245.62	$245.60	$245.60
Purchase #7	$16.47	12.445%	$18.5197	$18.52	$18.50	$18.50
7 purchase totals =	$1,095.75		$1,189.2367	$1,189.23	$1,189.25	$1,189.10