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	$231.43	13.416%	$262.4786	$262.48	$262.50	$262.50
Purchase #2	$49.47	12.374%	$55.5914	$55.59	$55.60	$55.60
Purchase #3	$117.54	8.257%	$127.2453	$127.25	$127.25	$127.20
Purchase #4	$53.64	3.392%	$55.4595	$55.46	$55.45	$55.50
Purchase #5	$232.92	10.344%	$257.0132	$257.01	$257.00	$257.00
Purchase #6	$72.53	7.318%	$77.8377	$77.84	$77.85	$77.80
Purchase #7	$110.73	11.338%	$123.2846	$123.28	$123.30	$123.30
7 purchase totals =	$868.26		$958.9103	$958.91	$958.95	$958.90