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	$57.47	9.479%	$62.9176	$62.92	$62.90	$62.90
Purchase #2	$31.74	10.416%	$35.046	$35.05	$35.05	$35.00
Purchase #3	$122.36	3.317%	$126.4187	$126.42	$126.40	$126.40
Purchase #4	$137.49	5.480%	$145.0245	$145.02	$145.00	$145.00
Purchase #5	$143.54	6.161%	$152.3835	$152.38	$152.40	$152.40
Purchase #6	$74.74	4.861%	$78.3731	$78.37	$78.35	$78.40
Purchase #7	$112.38	9.772%	$123.3618	$123.36	$123.35	$123.40
7 purchase totals =	$679.72		$723.5252	$723.52	$723.45	$723.50