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	$75.72	7.289%	$81.2392	$81.24	$81.25	$81.20
Purchase #2	$205.51	5.326%	$216.4555	$216.46	$216.45	$216.50
Purchase #3	$27.86	3.302%	$28.7799	$28.78	$28.80	$28.80
Purchase #4	$36.58	11.359%	$40.7351	$40.74	$40.75	$40.70
Purchase #5	$40.56	7.415%	$43.5675	$43.57	$43.55	$43.60
Purchase #6	$31.99	11.237%	$35.5847	$35.58	$35.60	$35.60
Purchase #7	$78.35	11.321%	$87.22	$87.22	$87.20	$87.20
7 purchase totals =	$496.57		$533.5819	$533.59	$533.60	$533.60