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	$117.36	11.414%	$130.7555	$130.76	$130.75	$130.80
Purchase #2	$47.83	12.667%	$53.8886	$53.89	$53.90	$53.90
Purchase #3	$117.83	12.441%	$132.4892	$132.49	$132.50	$132.50
Purchase #4	$38.83	10.108%	$42.7549	$42.75	$42.75	$42.80
Purchase #5	$124.63	10.684%	$137.9455	$137.95	$137.95	$137.90
Purchase #6	$62.64	3.411%	$64.7767	$64.78	$64.80	$64.80
Purchase #7	$8.54	4.282%	$8.9057	$8.91	$8.90	$8.90
7 purchase totals =	$517.66		$571.5161	$571.53	$571.55	$571.60