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	$68.93	5.347%	$72.6157	$72.62	$72.60	$72.60
Purchase #2	$38.69	12.108%	$43.3746	$43.37	$43.35	$43.40
Purchase #3	$232.97	12.199%	$261.39	$261.39	$261.40	$261.40
Purchase #4	$95.61	7.739%	$103.0093	$103.01	$103.00	$103.00
Purchase #5	$68.32	13.571%	$77.5917	$77.59	$77.60	$77.60
Purchase #6	$97.72	6.442%	$104.0151	$104.02	$104.00	$104.00
Purchase #7	$142.78	8.372%	$154.7335	$154.73	$154.75	$154.70
7 purchase totals =	$745.02		$816.7299	$816.73	$816.70	$816.70