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	$118.72	4.279%	$123.8	$123.80	$123.80	$123.80
Purchase #2	$141.62	7.266%	$151.9101	$151.91	$151.90	$151.90
Purchase #3	$208.48	6.811%	$222.6796	$222.68	$222.70	$222.70
Purchase #4	$39.91	10.120%	$43.9489	$43.95	$43.95	$43.90
Purchase #5	$41.66	8.823%	$45.3357	$45.34	$45.35	$45.30
Purchase #6	$189.67	6.416%	$201.8392	$201.84	$201.85	$201.80
Purchase #7	$68.32	6.710%	$72.9043	$72.90	$72.90	$72.90
7 purchase totals =	$808.38		$862.4178	$862.42	$862.45	$862.30