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	$171.71	11.468%	$191.4017	$191.40	$191.40	$191.40
Purchase #2	$126.57	5.567%	$133.6162	$133.62	$133.60	$133.60
Purchase #3	$31.75	5.516%	$33.5013	$33.50	$33.50	$33.50
Purchase #4	$21.79	8.520%	$23.6465	$23.65	$23.65	$23.60
Purchase #5	$29.96	3.499%	$31.0083	$31.01	$31.00	$31.00
Purchase #6	$57.78	3.687%	$59.9103	$59.91	$59.90	$59.90
Purchase #7	$40.42	5.485%	$42.637	$42.64	$42.65	$42.60
7 purchase totals =	$479.98		$515.7213	$515.73	$515.70	$515.60