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	$140.47	8.798%	$152.8286	$152.83	$152.85	$152.80
Purchase #2	$9.98	11.819%	$11.1595	$11.16	$11.15	$11.20
Purchase #3	$204.63	9.117%	$223.2861	$223.29	$223.30	$223.30
Purchase #4	$113.27	6.746%	$120.9112	$120.91	$120.90	$120.90
Purchase #5	$38.54	9.793%	$42.3142	$42.31	$42.30	$42.30
Purchase #6	$127.47	7.680%	$137.2597	$137.26	$137.25	$137.30
Purchase #7	$138.78	13.408%	$157.3876	$157.39	$157.40	$157.40
7 purchase totals =	$773.14		$845.1469	$845.15	$845.15	$845.20