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	$161.95	12.799%	$182.678	$182.68	$182.70	$182.70
Purchase #2	$138.56	8.278%	$150.03	$150.03	$150.05	$150.00
Purchase #3	$85.75	4.838%	$89.8986	$89.90	$89.90	$89.90
Purchase #4	$132.43	12.213%	$148.6037	$148.60	$148.60	$148.60
Purchase #5	$61.60	11.538%	$68.7074	$68.71	$68.70	$68.70
Purchase #6	$150.47	9.272%	$164.4216	$164.42	$164.40	$164.40
Purchase #7	$60.40	10.560%	$66.7782	$66.78	$66.80	$66.80
7 purchase totals =	$791.16		$871.1175	$871.12	$871.15	$871.10