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	$175.97	3.381%	$181.9195	$181.92	$181.90	$181.90
Purchase #2	$29.77	7.866%	$32.1117	$32.11	$32.10	$32.10
Purchase #3	$41.35	5.170%	$43.4878	$43.49	$43.50	$43.50
Purchase #4	$38.49	13.619%	$43.732	$43.73	$43.75	$43.70
Purchase #5	$36.52	3.576%	$37.826	$37.83	$37.85	$37.80
Purchase #6	$181.32	9.257%	$198.1048	$198.10	$198.10	$198.10
Purchase #7	$160.46	8.220%	$173.6498	$173.65	$173.65	$173.60
7 purchase totals =	$663.88		$710.8316	$710.83	$710.85	$710.70