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	$241.27	5.831%	$255.3385	$255.34	$255.35	$255.30
Purchase #2	$81.79	5.355%	$86.1699	$86.17	$86.15	$86.20
Purchase #3	$30.94	3.470%	$32.0136	$32.01	$32.00	$32.00
Purchase #4	$93.67	6.196%	$99.4738	$99.47	$99.45	$99.50
Purchase #5	$50.78	11.568%	$56.6542	$56.65	$56.65	$56.70
Purchase #6	$103.28	11.226%	$114.8742	$114.87	$114.85	$114.90
Purchase #7	$46.73	6.240%	$49.646	$49.65	$49.65	$49.60
7 purchase totals =	$648.46		$694.1702	$694.16	$694.10	$694.20