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	$185.47	13.437%	$210.3916	$210.39	$210.40	$210.40
Purchase #2	$80.95	11.214%	$90.0277	$90.03	$90.05	$90.00
Purchase #3	$21.48	7.243%	$23.0358	$23.04	$23.05	$23.00
Purchase #4	$188.95	12.529%	$212.6235	$212.62	$212.60	$212.60
Purchase #5	$165.45	10.502%	$182.8256	$182.83	$182.85	$182.80
Purchase #6	$107.40	11.621%	$119.881	$119.88	$119.90	$119.90
Purchase #7	$216.59	3.634%	$224.4609	$224.46	$224.45	$224.50
7 purchase totals =	$966.29		$1,063.2461	$1,063.25	$1,063.30	$1,063.20