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	$43.48	5.510%	$45.8757	$45.88	$45.90	$45.90
Purchase #2	$149.82	8.749%	$162.9278	$162.93	$162.95	$162.90
Purchase #3	$168.43	6.380%	$179.1758	$179.18	$179.20	$179.20
Purchase #4	$209.55	6.856%	$223.9167	$223.92	$223.90	$223.90
Purchase #5	$23.57	8.653%	$25.6095	$25.61	$25.60	$25.60
Purchase #6	$74.69	10.573%	$82.587	$82.59	$82.60	$82.60
Purchase #7	$161.69	8.612%	$175.6147	$175.61	$175.60	$175.60
7 purchase totals =	$831.23		$895.7072	$895.72	$895.75	$895.70