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	$112.86	10.829%	$125.0816	$125.08	$125.10	$125.10
Purchase #2	$11.53	7.605%	$12.4069	$12.41	$12.40	$12.40
Purchase #3	$146.63	6.575%	$156.2709	$156.27	$156.25	$156.30
Purchase #4	$132.43	10.405%	$146.2093	$146.21	$146.20	$146.20
Purchase #5	$113.53	9.133%	$123.8987	$123.90	$123.90	$123.90
Purchase #6	$131.76	6.646%	$140.5168	$140.52	$140.50	$140.50
Purchase #7	$51.35	8.789%	$55.8632	$55.86	$55.85	$55.90
7 purchase totals =	$700.09		$760.2474	$760.25	$760.20	$760.30