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	$69.36	11.860%	$77.5861	$77.59	$77.60	$77.60
Purchase #2	$83.96	13.279%	$95.109	$95.11	$95.10	$95.10
Purchase #3	$175.71	5.795%	$185.8924	$185.89	$185.90	$185.90
Purchase #4	$40.40	11.643%	$45.1038	$45.10	$45.10	$45.10
Purchase #5	$140.60	11.545%	$156.8323	$156.83	$156.85	$156.80
Purchase #6	$53.57	12.166%	$60.0873	$60.09	$60.10	$60.10
Purchase #7	$81.62	6.753%	$87.1318	$87.13	$87.15	$87.10
7 purchase totals =	$645.22		$707.7427	$707.74	$707.80	$707.70