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	$119.70	5.872%	$126.7288	$126.73	$126.75	$126.70
Purchase #2	$182.55	9.431%	$199.7663	$199.77	$199.75	$199.80
Purchase #3	$44.34	9.435%	$48.5235	$48.52	$48.50	$48.50
Purchase #4	$228.69	6.219%	$242.9122	$242.91	$242.90	$242.90
Purchase #5	$22.41	9.338%	$24.5026	$24.50	$24.50	$24.50
Purchase #6	$71.40	10.555%	$78.9363	$78.94	$78.95	$78.90
Purchase #7	$36.59	13.477%	$41.5212	$41.52	$41.50	$41.50
7 purchase totals =	$705.68		$762.8909	$762.89	$762.85	$762.80