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	$45.61	3.593%	$47.2488	$47.25	$47.25	$47.20
Purchase #2	$160.75	4.829%	$168.5126	$168.51	$168.50	$168.50
Purchase #3	$64.75	10.760%	$71.7171	$71.72	$71.70	$71.70
Purchase #4	$9.59	12.476%	$10.7864	$10.79	$10.80	$10.80
Purchase #5	$136.52	11.690%	$152.4792	$152.48	$152.50	$152.50
Purchase #6	$175.52	11.572%	$195.8312	$195.83	$195.85	$195.80
Purchase #7	$112.62	8.337%	$122.0091	$122.01	$122.00	$122.00
7 purchase totals =	$705.36		$768.5844	$768.59	$768.60	$768.50