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	$148.76	7.440%	$159.8277	$159.83	$159.85	$159.80
Purchase #2	$140.35	9.298%	$153.3997	$153.40	$153.40	$153.40
Purchase #3	$136.48	3.225%	$140.8815	$140.88	$140.90	$140.90
Purchase #4	$162.51	12.290%	$182.4825	$182.48	$182.50	$182.50
Purchase #5	$166.70	13.840%	$189.7713	$189.77	$189.75	$189.80
Purchase #6	$96.51	5.838%	$102.1443	$102.14	$102.15	$102.10
Purchase #7	$49.66	6.618%	$52.9465	$52.95	$52.95	$52.90
7 purchase totals =	$900.97		$981.4535	$981.45	$981.50	$981.40