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	$201.47	7.795%	$217.1746	$217.17	$217.15	$217.20
Purchase #2	$212.98	4.292%	$222.1211	$222.12	$222.10	$222.10
Purchase #3	$245.85	6.478%	$261.7762	$261.78	$261.80	$261.80
Purchase #4	$109.93	4.559%	$114.9417	$114.94	$114.95	$114.90
Purchase #5	$169.26	9.787%	$185.8255	$185.83	$185.85	$185.80
Purchase #6	$14.83	11.341%	$16.5119	$16.51	$16.50	$16.50
Purchase #7	$35.69	4.849%	$37.4206	$37.42	$37.40	$37.40
7 purchase totals =	$990.01		$1,055.7716	$1,055.77	$1,055.75	$1,055.70