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	$175.50	12.709%	$197.8043	$197.80	$197.80	$197.80
Purchase #2	$162.90	12.809%	$183.7659	$183.77	$183.75	$183.80
Purchase #3	$129.50	8.200%	$140.119	$140.12	$140.10	$140.10
Purchase #4	$96.61	9.567%	$105.8527	$105.85	$105.85	$105.90
Purchase #5	$10.29	6.105%	$10.9182	$10.92	$10.90	$10.90
Purchase #6	$229.59	12.589%	$258.4931	$258.49	$258.50	$258.50
Purchase #7	$125.89	4.745%	$131.8635	$131.86	$131.85	$131.90
7 purchase totals =	$930.28		$1,028.8167	$1,028.81	$1,028.75	$1,028.90