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	$95.47	6.606%	$101.7767	$101.78	$101.80	$101.80
Purchase #2	$89.37	4.496%	$93.3881	$93.39	$93.40	$93.40
Purchase #3	$48.84	12.632%	$55.0095	$55.01	$55.00	$55.00
Purchase #4	$145.67	3.727%	$151.0991	$151.10	$151.10	$151.10
Purchase #5	$196.66	13.238%	$222.6939	$222.69	$222.70	$222.70
Purchase #6	$249.38	6.643%	$265.9463	$265.95	$265.95	$265.90
Purchase #7	$49.44	12.315%	$55.5285	$55.53	$55.55	$55.50
7 purchase totals =	$874.83		$945.4421	$945.45	$945.50	$945.40