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	$204.88	9.168%	$223.6634	$223.66	$223.65	$223.70
Purchase #2	$34.75	3.205%	$35.8637	$35.86	$35.85	$35.90
Purchase #3	$100.95	3.708%	$104.6932	$104.69	$104.70	$104.70
Purchase #4	$236.73	11.213%	$263.2745	$263.27	$263.25	$263.30
Purchase #5	$213.83	4.478%	$223.4053	$223.41	$223.40	$223.40
Purchase #6	$151.37	11.395%	$168.6186	$168.62	$168.60	$168.60
Purchase #7	$158.48	7.481%	$170.3359	$170.34	$170.35	$170.30
7 purchase totals =	$1,100.99		$1,189.8546	$1,189.85	$1,189.80	$1,189.90