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	$58.80	4.317%	$61.3384	$61.34	$61.35	$61.30
Purchase #2	$237.59	5.183%	$249.9043	$249.90	$249.90	$249.90
Purchase #3	$59.67	12.832%	$67.3269	$67.33	$67.35	$67.30
Purchase #4	$60.76	13.196%	$68.7779	$68.78	$68.80	$68.80
Purchase #5	$146.49	5.354%	$154.3331	$154.33	$154.35	$154.30
Purchase #6	$105.26	11.123%	$116.9681	$116.97	$116.95	$117.00
Purchase #7	$38.52	10.507%	$42.5673	$42.57	$42.55	$42.60
7 purchase totals =	$707.09		$761.2160	$761.22	$761.25	$761.20