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	$46.28	11.176%	$51.4523	$51.45	$51.45	$51.50
Purchase #2	$25.48	13.345%	$28.8803	$28.88	$28.90	$28.90
Purchase #3	$14.44	9.731%	$15.8452	$15.85	$15.85	$15.80
Purchase #4	$152.84	10.551%	$168.9661	$168.97	$168.95	$169.00
Purchase #5	$141.48	6.438%	$150.5885	$150.59	$150.60	$150.60
Purchase #6	$142.84	12.164%	$160.2151	$160.22	$160.20	$160.20
Purchase #7	$29.35	10.197%	$32.3428	$32.34	$32.35	$32.30
7 purchase totals =	$552.71		$608.2903	$608.30	$608.30	$608.30