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	$170.35	9.453%	$186.4532	$186.45	$186.45	$186.50
Purchase #2	$108.74	11.500%	$121.2451	$121.25	$121.25	$121.20
Purchase #3	$98.38	13.167%	$111.3337	$111.33	$111.35	$111.30
Purchase #4	$227.59	6.153%	$241.5936	$241.59	$241.60	$241.60
Purchase #5	$127.89	9.512%	$140.0549	$140.05	$140.05	$140.10
Purchase #6	$109.45	13.665%	$124.4063	$124.41	$124.40	$124.40
Purchase #7	$64.38	10.412%	$71.0832	$71.08	$71.10	$71.10
7 purchase totals =	$906.78		$996.1700	$996.16	$996.20	$996.20