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	$76.98	12.740%	$86.7873	$86.79	$86.80	$86.80
Purchase #2	$158.27	3.669%	$164.0769	$164.08	$164.10	$164.10
Purchase #3	$133.36	11.633%	$148.8738	$148.87	$148.85	$148.90
Purchase #4	$156.28	8.380%	$169.3763	$169.38	$169.40	$169.40
Purchase #5	$127.74	3.219%	$131.852	$131.85	$131.85	$131.90
Purchase #6	$66.52	8.330%	$72.0611	$72.06	$72.05	$72.10
Purchase #7	$22.63	5.692%	$23.9181	$23.92	$23.90	$23.90
7 purchase totals =	$741.78		$796.9455	$796.95	$796.95	$797.10