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	$149.72	13.841%	$170.4427	$170.44	$170.45	$170.40
Purchase #2	$46.48	5.151%	$48.8742	$48.87	$48.85	$48.90
Purchase #3	$53.25	12.519%	$59.9164	$59.92	$59.90	$59.90
Purchase #4	$99.88	11.552%	$111.4181	$111.42	$111.40	$111.40
Purchase #5	$192.56	4.807%	$201.8164	$201.82	$201.80	$201.80
Purchase #6	$70.69	7.637%	$76.0886	$76.09	$76.10	$76.10
Purchase #7	$37.25	6.810%	$39.7867	$39.79	$39.80	$39.80
7 purchase totals =	$649.83		$708.3431	$708.35	$708.30	$708.30