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	$142.53	6.355%	$151.5878	$151.59	$151.60	$151.60
Purchase #2	$87.69	7.533%	$94.2957	$94.30	$94.30	$94.30
Purchase #3	$217.51	7.799%	$234.4736	$234.47	$234.45	$234.50
Purchase #4	$148.94	10.382%	$164.403	$164.40	$164.40	$164.40
Purchase #5	$159.77	3.753%	$165.7662	$165.77	$165.75	$165.80
Purchase #6	$88.48	8.403%	$95.915	$95.92	$95.90	$95.90
Purchase #7	$73.86	3.655%	$76.5596	$76.56	$76.55	$76.60
7 purchase totals =	$918.78		$983.0009	$983.01	$982.95	$983.10