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	$232.86	12.407%	$261.7509	$261.75	$261.75	$261.80
Purchase #2	$38.50	4.670%	$40.298	$40.30	$40.30	$40.30
Purchase #3	$240.76	12.787%	$271.546	$271.55	$271.55	$271.50
Purchase #4	$213.69	9.127%	$233.1935	$233.19	$233.20	$233.20
Purchase #5	$37.85	11.431%	$42.1766	$42.18	$42.20	$42.20
Purchase #6	$56.72	5.672%	$59.9372	$59.94	$59.95	$59.90
Purchase #7	$148.86	10.587%	$164.6198	$164.62	$164.60	$164.60
7 purchase totals =	$969.24		$1,073.5220	$1,073.53	$1,073.55	$1,073.50