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	$141.46	6.441%	$150.5714	$150.57	$150.55	$150.60
Purchase #2	$135.54	11.705%	$151.405	$151.41	$151.40	$151.40
Purchase #3	$20.69	4.628%	$21.6475	$21.65	$21.65	$21.60
Purchase #4	$73.25	12.827%	$82.6458	$82.65	$82.65	$82.60
Purchase #5	$37.64	11.257%	$41.8771	$41.88	$41.90	$41.90
Purchase #6	$132.25	10.621%	$146.2963	$146.30	$146.30	$146.30
Purchase #7	$58.49	7.660%	$62.9703	$62.97	$62.95	$63.00
7 purchase totals =	$599.32		$657.4134	$657.43	$657.40	$657.40