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	$40.56	3.186%	$41.8522	$41.85	$41.85	$41.90
Purchase #2	$39.44	5.654%	$41.6699	$41.67	$41.65	$41.70
Purchase #3	$82.39	11.860%	$92.1615	$92.16	$92.15	$92.20
Purchase #4	$142.51	9.116%	$155.5012	$155.50	$155.50	$155.50
Purchase #5	$41.62	10.389%	$45.9439	$45.94	$45.95	$45.90
Purchase #6	$197.50	6.707%	$210.7463	$210.75	$210.75	$210.70
Purchase #7	$245.85	8.832%	$267.5635	$267.56	$267.55	$267.60
7 purchase totals =	$789.87		$855.4385	$855.43	$855.40	$855.50