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	$196.54	9.775%	$215.7518	$215.75	$215.75	$215.80
Purchase #2	$96.66	12.813%	$109.045	$109.05	$109.05	$109.00
Purchase #3	$95.54	4.227%	$99.5785	$99.58	$99.60	$99.60
Purchase #4	$90.98	10.588%	$100.613	$100.61	$100.60	$100.60
Purchase #5	$33.35	3.233%	$34.4282	$34.43	$34.45	$34.40
Purchase #6	$125.36	13.637%	$142.4553	$142.46	$142.45	$142.50
Purchase #7	$42.55	5.803%	$45.0192	$45.02	$45.00	$45.00
7 purchase totals =	$680.98		$746.8910	$746.90	$746.90	$746.90