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	$115.83	8.125%	$125.2412	$125.24	$125.25	$125.20
Purchase #2	$74.96	13.437%	$85.0324	$85.03	$85.05	$85.00
Purchase #3	$19.91	3.486%	$20.6041	$20.60	$20.60	$20.60
Purchase #4	$29.93	12.278%	$33.6048	$33.60	$33.60	$33.60
Purchase #5	$196.39	8.701%	$213.4779	$213.48	$213.50	$213.50
Purchase #6	$150.94	11.601%	$168.4505	$168.45	$168.45	$168.50
Purchase #7	$199.89	9.638%	$219.1554	$219.16	$219.15	$219.20
7 purchase totals =	$787.85		$865.5663	$865.56	$865.60	$865.60