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	$56.78	11.438%	$63.2745	$63.27	$63.25	$63.30
Purchase #2	$143.94	8.759%	$156.5477	$156.55	$156.55	$156.50
Purchase #3	$42.25	7.865%	$45.573	$45.57	$45.55	$45.60
Purchase #4	$86.37	11.322%	$96.1488	$96.15	$96.15	$96.10
Purchase #5	$201.66	10.307%	$222.4451	$222.45	$222.45	$222.40
Purchase #6	$31.77	9.427%	$34.765	$34.77	$34.75	$34.80
Purchase #7	$168.92	4.502%	$176.5248	$176.52	$176.50	$176.50
7 purchase totals =	$731.69		$795.2789	$795.28	$795.20	$795.20