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	$189.38	13.800%	$215.5144	$215.51	$215.50	$215.50
Purchase #2	$137.81	13.576%	$156.5191	$156.52	$156.50	$156.50
Purchase #3	$101.93	3.455%	$105.4517	$105.45	$105.45	$105.50
Purchase #4	$196.87	3.433%	$203.6285	$203.63	$203.65	$203.60
Purchase #5	$16.26	11.544%	$18.1371	$18.14	$18.15	$18.10
Purchase #6	$150.79	4.476%	$157.5394	$157.54	$157.55	$157.50
Purchase #7	$145.41	4.794%	$152.381	$152.38	$152.40	$152.40
7 purchase totals =	$938.45		$1,009.1712	$1,009.17	$1,009.20	$1,009.10