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	$31.39	13.472%	$35.6189	$35.62	$35.60	$35.60
Purchase #2	$105.82	9.402%	$115.7692	$115.77	$115.75	$115.80
Purchase #3	$84.55	11.190%	$94.0111	$94.01	$94.00	$94.00
Purchase #4	$52.92	12.474%	$59.5212	$59.52	$59.50	$59.50
Purchase #5	$57.48	11.372%	$64.0166	$64.02	$64.00	$64.00
Purchase #6	$11.91	8.198%	$12.8864	$12.89	$12.90	$12.90
Purchase #7	$94.35	8.840%	$102.6905	$102.69	$102.70	$102.70
7 purchase totals =	$438.42		$484.5139	$484.52	$484.45	$484.50