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	$247.71	7.695%	$266.7713	$266.77	$266.75	$266.80
Purchase #2	$242.36	13.653%	$275.4494	$275.45	$275.45	$275.40
Purchase #3	$175.87	7.817%	$189.6178	$189.62	$189.60	$189.60
Purchase #4	$151.63	11.850%	$169.5982	$169.60	$169.60	$169.60
Purchase #5	$238.44	7.492%	$256.3039	$256.30	$256.30	$256.30
Purchase #6	$246.66	3.237%	$254.6444	$254.64	$254.65	$254.60
Purchase #7	$150.62	5.814%	$159.377	$159.38	$159.40	$159.40
7 purchase totals =	$1,453.29		$1,571.7620	$1,571.76	$1,571.75	$1,571.70