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	$176.49	6.109%	$187.2718	$187.27	$187.25	$187.30
Purchase #2	$123.26	7.500%	$132.5045	$132.50	$132.50	$132.50
Purchase #3	$89.85	13.674%	$102.1361	$102.14	$102.15	$102.10
Purchase #4	$116.76	5.524%	$123.2098	$123.21	$123.20	$123.20
Purchase #5	$86.72	4.851%	$90.9268	$90.93	$90.95	$90.90
Purchase #6	$137.55	9.533%	$150.6626	$150.66	$150.65	$150.70
Purchase #7	$73.94	4.310%	$77.1268	$77.13	$77.15	$77.10
7 purchase totals =	$804.57		$863.8384	$863.84	$863.85	$863.80