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	$177.27	12.715%	$199.8099	$199.81	$199.80	$199.80
Purchase #2	$29.69	7.160%	$31.8158	$31.82	$31.80	$31.80
Purchase #3	$43.79	10.776%	$48.5088	$48.51	$48.50	$48.50
Purchase #4	$184.50	6.273%	$196.0737	$196.07	$196.05	$196.10
Purchase #5	$9.76	5.293%	$10.2766	$10.28	$10.30	$10.30
Purchase #6	$30.42	7.619%	$32.7377	$32.74	$32.75	$32.70
Purchase #7	$248.38	6.691%	$264.9991	$265.00	$265.00	$265.00
7 purchase totals =	$723.81		$784.2216	$784.23	$784.20	$784.20