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	$31.86	9.248%	$34.8064	$34.81	$34.80	$34.80
Purchase #2	$164.45	11.289%	$183.0148	$183.01	$183.00	$183.00
Purchase #3	$127.39	11.306%	$141.7927	$141.79	$141.80	$141.80
Purchase #4	$216.39	7.318%	$232.2254	$232.23	$232.25	$232.20
Purchase #5	$214.86	8.502%	$233.1274	$233.13	$233.15	$233.10
Purchase #6	$73.73	6.346%	$78.4089	$78.41	$78.40	$78.40
Purchase #7	$150.48	5.121%	$158.1861	$158.19	$158.20	$158.20
7 purchase totals =	$979.16		$1,061.5617	$1,061.57	$1,061.60	$1,061.50