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	$60.87	10.633%	$67.3423	$67.34	$67.35	$67.30
Purchase #2	$241.90	12.260%	$271.5569	$271.56	$271.55	$271.60
Purchase #3	$104.84	12.816%	$118.2763	$118.28	$118.30	$118.30
Purchase #4	$153.65	5.761%	$162.5018	$162.50	$162.50	$162.50
Purchase #5	$179.25	6.639%	$191.1504	$191.15	$191.15	$191.20
Purchase #6	$187.90	10.645%	$207.902	$207.90	$207.90	$207.90
Purchase #7	$70.53	10.395%	$77.8616	$77.86	$77.85	$77.90
7 purchase totals =	$998.94		$1,096.5913	$1,096.59	$1,096.60	$1,096.70