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	$125.48	6.865%	$134.0942	$134.09	$134.10	$134.10
Purchase #2	$40.91	3.369%	$42.2883	$42.29	$42.30	$42.30
Purchase #3	$29.77	7.146%	$31.8974	$31.90	$31.90	$31.90
Purchase #4	$75.98	8.329%	$82.3084	$82.31	$82.30	$82.30
Purchase #5	$94.54	8.705%	$102.7697	$102.77	$102.75	$102.80
Purchase #6	$219.89	3.604%	$227.8148	$227.81	$227.80	$227.80
Purchase #7	$162.61	8.595%	$176.5863	$176.59	$176.60	$176.60
7 purchase totals =	$749.18		$797.7591	$797.76	$797.75	$797.80