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	$116.80	13.790%	$132.9067	$132.91	$132.90	$132.90
Purchase #2	$188.75	4.325%	$196.9134	$196.91	$196.90	$196.90
Purchase #3	$95.25	3.793%	$98.8628	$98.86	$98.85	$98.90
Purchase #4	$211.36	3.355%	$218.4511	$218.45	$218.45	$218.50
Purchase #5	$36.26	9.149%	$39.5774	$39.58	$39.60	$39.60
Purchase #6	$130.86	12.691%	$147.4674	$147.47	$147.45	$147.50
Purchase #7	$66.51	7.732%	$71.6526	$71.65	$71.65	$71.70
7 purchase totals =	$845.79		$905.8314	$905.83	$905.80	$906.00