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	$190.85	11.451%	$212.7042	$212.70	$212.70	$212.70
Purchase #2	$165.43	8.691%	$179.8075	$179.81	$179.80	$179.80
Purchase #3	$51.92	5.386%	$54.7164	$54.72	$54.70	$54.70
Purchase #4	$94.59	4.689%	$99.0253	$99.03	$99.05	$99.00
Purchase #5	$243.32	12.344%	$273.3554	$273.36	$273.35	$273.40
Purchase #6	$222.74	9.263%	$243.3724	$243.37	$243.35	$243.40
Purchase #7	$137.72	5.655%	$145.5081	$145.51	$145.50	$145.50
7 purchase totals =	$1,106.57		$1,208.4893	$1,208.50	$1,208.45	$1,208.50