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	$31.93	8.440%	$34.6249	$34.62	$34.60	$34.60
Purchase #2	$116.56	5.606%	$123.0944	$123.09	$123.10	$123.10
Purchase #3	$181.99	12.438%	$204.6259	$204.63	$204.65	$204.60
Purchase #4	$100.35	5.521%	$105.8903	$105.89	$105.90	$105.90
Purchase #5	$106.52	6.422%	$113.3607	$113.36	$113.35	$113.40
Purchase #6	$201.71	10.665%	$223.2224	$223.22	$223.20	$223.20
Purchase #7	$117.53	7.734%	$126.6198	$126.62	$126.60	$126.60
7 purchase totals =	$856.59		$931.4384	$931.43	$931.40	$931.40