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	$190.33	9.759%	$208.9043	$208.90	$208.90	$208.90
Purchase #2	$90.62	10.143%	$99.8116	$99.81	$99.80	$99.80
Purchase #3	$238.54	3.429%	$246.7195	$246.72	$246.70	$246.70
Purchase #4	$224.87	8.692%	$244.4157	$244.42	$244.40	$244.40
Purchase #5	$26.53	4.122%	$27.6236	$27.62	$27.60	$27.60
Purchase #6	$116.89	8.661%	$127.0138	$127.01	$127.00	$127.00
Purchase #7	$48.44	3.412%	$50.0928	$50.09	$50.10	$50.10
7 purchase totals =	$936.22		$1,004.5813	$1,004.57	$1,004.50	$1,004.50