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	$120.77	8.381%	$130.8917	$130.89	$130.90	$130.90
Purchase #2	$205.66	13.620%	$233.6709	$233.67	$233.65	$233.70
Purchase #3	$192.43	3.306%	$198.7917	$198.79	$198.80	$198.80
Purchase #4	$208.31	12.145%	$233.6092	$233.61	$233.60	$233.60
Purchase #5	$42.91	6.789%	$45.8232	$45.82	$45.80	$45.80
Purchase #6	$232.93	5.329%	$245.3428	$245.34	$245.35	$245.30
Purchase #7	$40.73	11.735%	$45.5097	$45.51	$45.50	$45.50
7 purchase totals =	$1,043.74		$1,133.6392	$1,133.63	$1,133.60	$1,133.60