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	$53.70	6.867%	$57.3876	$57.39	$57.40	$57.40
Purchase #2	$152.53	6.448%	$162.3651	$162.37	$162.35	$162.40
Purchase #3	$214.72	11.441%	$239.2861	$239.29	$239.30	$239.30
Purchase #4	$46.81	7.681%	$50.4055	$50.41	$50.40	$50.40
Purchase #5	$36.42	7.677%	$39.216	$39.22	$39.20	$39.20
Purchase #6	$176.51	8.504%	$191.5204	$191.52	$191.50	$191.50
Purchase #7	$214.54	12.455%	$241.261	$241.26	$241.25	$241.30
7 purchase totals =	$895.23		$981.4417	$981.46	$981.40	$981.50