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	$198.27	3.473%	$205.1559	$205.16	$205.15	$205.20
Purchase #2	$220.63	13.714%	$250.8872	$250.89	$250.90	$250.90
Purchase #3	$133.26	13.128%	$150.7544	$150.75	$150.75	$150.80
Purchase #4	$9.81	11.117%	$10.9006	$10.90	$10.90	$10.90
Purchase #5	$224.97	4.720%	$235.5886	$235.59	$235.60	$235.60
Purchase #6	$113.57	13.510%	$128.9133	$128.91	$128.90	$128.90
Purchase #7	$45.99	13.164%	$52.0441	$52.04	$52.05	$52.00
7 purchase totals =	$946.50		$1,034.2441	$1,034.24	$1,034.25	$1,034.30