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	$115.98	9.725%	$127.2591	$127.26	$127.25	$127.30
Purchase #2	$53.48	7.222%	$57.3423	$57.34	$57.35	$57.30
Purchase #3	$113.91	4.477%	$119.0098	$119.01	$119.00	$119.00
Purchase #4	$73.29	4.758%	$76.7771	$76.78	$76.80	$76.80
Purchase #5	$107.78	8.423%	$116.8583	$116.86	$116.85	$116.90
Purchase #6	$137.65	3.539%	$142.5214	$142.52	$142.50	$142.50
Purchase #7	$52.26	5.732%	$55.2555	$55.26	$55.25	$55.30
7 purchase totals =	$654.35		$695.0235	$695.03	$695.00	$695.10