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	$243.47	7.421%	$261.5379	$261.54	$261.55	$261.50
Purchase #2	$91.83	8.529%	$99.6622	$99.66	$99.65	$99.70
Purchase #3	$227.31	12.606%	$255.9647	$255.96	$255.95	$256.00
Purchase #4	$212.77	10.723%	$235.5853	$235.59	$235.60	$235.60
Purchase #5	$87.92	9.758%	$96.4992	$96.50	$96.50	$96.50
Purchase #6	$41.96	9.754%	$46.0528	$46.05	$46.05	$46.10
Purchase #7	$68.95	3.349%	$71.2591	$71.26	$71.25	$71.30
7 purchase totals =	$974.21		$1,066.5612	$1,066.56	$1,066.55	$1,066.70