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	$81.63	10.343%	$90.073	$90.07	$90.05	$90.10
Purchase #2	$72.26	7.160%	$77.4338	$77.43	$77.45	$77.40
Purchase #3	$69.38	5.709%	$73.3409	$73.34	$73.35	$73.30
Purchase #4	$78.58	5.395%	$82.8194	$82.82	$82.80	$82.80
Purchase #5	$204.27	7.775%	$220.152	$220.15	$220.15	$220.20
Purchase #6	$119.76	13.773%	$136.2545	$136.25	$136.25	$136.30
Purchase #7	$214.68	3.631%	$222.475	$222.48	$222.50	$222.50
7 purchase totals =	$840.56		$902.5486	$902.54	$902.55	$902.60