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	$162.62	11.535%	$181.3782	$181.38	$181.40	$181.40
Purchase #2	$200.80	11.850%	$224.5948	$224.59	$224.60	$224.60
Purchase #3	$183.61	13.587%	$208.5571	$208.56	$208.55	$208.60
Purchase #4	$38.65	10.240%	$42.6078	$42.61	$42.60	$42.60
Purchase #5	$122.77	3.625%	$127.2204	$127.22	$127.20	$127.20
Purchase #6	$31.30	3.497%	$32.3946	$32.39	$32.40	$32.40
Purchase #7	$95.44	11.688%	$106.595	$106.60	$106.60	$106.60
7 purchase totals =	$835.19		$923.3479	$923.35	$923.35	$923.40