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	$171.48	11.770%	$191.6632	$191.66	$191.65	$191.70
Purchase #2	$120.39	5.340%	$126.8188	$126.82	$126.80	$126.80
Purchase #3	$196.94	5.791%	$208.3448	$208.34	$208.35	$208.30
Purchase #4	$34.92	4.675%	$36.5525	$36.55	$36.55	$36.60
Purchase #5	$173.79	10.523%	$192.0779	$192.08	$192.10	$192.10
Purchase #6	$12.31	4.705%	$12.8892	$12.89	$12.90	$12.90
Purchase #7	$225.53	10.622%	$249.4858	$249.49	$249.50	$249.50
7 purchase totals =	$935.36		$1,017.8322	$1,017.83	$1,017.85	$1,017.90