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	$72.64	11.298%	$80.8469	$80.85	$80.85	$80.80
Purchase #2	$16.66	13.396%	$18.8918	$18.89	$18.90	$18.90
Purchase #3	$83.86	6.670%	$89.4535	$89.45	$89.45	$89.50
Purchase #4	$89.68	4.729%	$93.921	$93.92	$93.90	$93.90
Purchase #5	$81.28	6.301%	$86.4015	$86.40	$86.40	$86.40
Purchase #6	$137.83	13.856%	$156.9277	$156.93	$156.95	$156.90
Purchase #7	$8.59	4.502%	$8.9767	$8.98	$9.00	$9.00
7 purchase totals =	$490.54		$535.4191	$535.42	$535.45	$535.40