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	$38.47	4.796%	$40.315	$40.32	$40.30	$40.30
Purchase #2	$107.94	11.178%	$120.0055	$120.01	$120.00	$120.00
Purchase #3	$96.54	8.394%	$104.6436	$104.64	$104.65	$104.60
Purchase #4	$68.39	12.746%	$77.107	$77.11	$77.10	$77.10
Purchase #5	$72.91	5.354%	$76.8136	$76.81	$76.80	$76.80
Purchase #6	$92.86	8.675%	$100.9156	$100.92	$100.90	$100.90
Purchase #7	$96.31	9.855%	$105.8014	$105.80	$105.80	$105.80
7 purchase totals =	$573.42		$625.6017	$625.61	$625.55	$625.50