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	$182.89	9.515%	$200.292	$200.29	$200.30	$200.30
Purchase #2	$133.65	5.437%	$140.9166	$140.92	$140.90	$140.90
Purchase #3	$157.61	11.707%	$176.0614	$176.06	$176.05	$176.10
Purchase #4	$56.63	8.137%	$61.238	$61.24	$61.25	$61.20
Purchase #5	$198.59	10.185%	$218.8164	$218.82	$218.80	$218.80
Purchase #6	$145.51	9.534%	$159.3829	$159.38	$159.40	$159.40
Purchase #7	$141.44	8.297%	$153.1753	$153.18	$153.20	$153.20
7 purchase totals =	$1,016.32		$1,109.8826	$1,109.89	$1,109.90	$1,109.90