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	$84.48	3.532%	$87.4638	$87.46	$87.45	$87.50
Purchase #2	$19.84	10.294%	$21.8823	$21.88	$21.90	$21.90
Purchase #3	$92.47	7.621%	$99.5171	$99.52	$99.50	$99.50
Purchase #4	$169.83	5.757%	$179.6071	$179.61	$179.60	$179.60
Purchase #5	$233.81	9.827%	$256.7865	$256.79	$256.80	$256.80
Purchase #6	$122.88	7.116%	$131.6241	$131.62	$131.60	$131.60
Purchase #7	$53.53	8.490%	$58.0747	$58.07	$58.05	$58.10
7 purchase totals =	$776.84		$834.9556	$834.95	$834.90	$835.00