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	$59.28	9.366%	$64.8322	$64.83	$64.85	$64.80
Purchase #2	$131.76	11.257%	$146.5922	$146.59	$146.60	$146.60
Purchase #3	$149.57	11.351%	$166.5477	$166.55	$166.55	$166.50
Purchase #4	$103.83	10.297%	$114.5214	$114.52	$114.50	$114.50
Purchase #5	$159.31	5.405%	$167.9207	$167.92	$167.90	$167.90
Purchase #6	$182.43	10.191%	$201.0214	$201.02	$201.00	$201.00
Purchase #7	$141.44	4.873%	$148.3324	$148.33	$148.35	$148.30
7 purchase totals =	$927.62		$1,009.7680	$1,009.76	$1,009.75	$1,009.60