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	$111.71	7.735%	$120.3508	$120.35	$120.35	$120.40
Purchase #2	$184.93	3.584%	$191.5579	$191.56	$191.55	$191.60
Purchase #3	$163.56	11.310%	$182.0586	$182.06	$182.05	$182.10
Purchase #4	$24.43	3.554%	$25.2982	$25.30	$25.30	$25.30
Purchase #5	$26.89	5.599%	$28.3956	$28.40	$28.40	$28.40
Purchase #6	$164.59	9.866%	$180.8284	$180.83	$180.85	$180.80
Purchase #7	$160.51	7.143%	$171.9752	$171.98	$172.00	$172.00
7 purchase totals =	$836.62		$900.4647	$900.48	$900.50	$900.60