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	$32.41	9.407%	$35.4588	$35.46	$35.45	$35.50
Purchase #2	$11.75	11.609%	$13.1141	$13.11	$13.10	$13.10
Purchase #3	$30.67	7.329%	$32.9178	$32.92	$32.90	$32.90
Purchase #4	$115.67	11.560%	$129.0415	$129.04	$129.05	$129.00
Purchase #5	$37.70	6.231%	$40.0491	$40.05	$40.05	$40.00
Purchase #6	$18.83	3.481%	$19.4855	$19.49	$19.50	$19.50
Purchase #7	$79.77	13.856%	$90.8229	$90.82	$90.80	$90.80
7 purchase totals =	$326.80		$360.8897	$360.89	$360.85	$360.80