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	$62.95	12.471%	$70.8005	$70.80	$70.80	$70.80
Purchase #2	$80.41	12.457%	$90.4267	$90.43	$90.45	$90.40
Purchase #3	$33.85	11.375%	$37.7004	$37.70	$37.70	$37.70
Purchase #4	$22.53	6.548%	$24.0053	$24.01	$24.00	$24.00
Purchase #5	$94.75	5.582%	$100.0389	$100.04	$100.05	$100.00
Purchase #6	$96.80	5.535%	$102.1579	$102.16	$102.15	$102.20
Purchase #7	$91.51	4.609%	$95.7277	$95.73	$95.75	$95.70
7 purchase totals =	$482.80		$520.8574	$520.87	$520.90	$520.80