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	$192.32	9.842%	$211.2481	$211.25	$211.25	$211.20
Purchase #2	$196.39	3.693%	$203.6427	$203.64	$203.65	$203.60
Purchase #3	$211.81	9.174%	$231.2414	$231.24	$231.25	$231.20
Purchase #4	$161.63	11.782%	$180.6732	$180.67	$180.65	$180.70
Purchase #5	$43.60	4.190%	$45.4268	$45.43	$45.45	$45.40
Purchase #6	$97.39	8.735%	$105.897	$105.90	$105.90	$105.90
Purchase #7	$230.50	6.591%	$245.6923	$245.69	$245.70	$245.70
7 purchase totals =	$1,133.64		$1,223.8215	$1,223.82	$1,223.85	$1,223.70