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	$139.73	11.218%	$155.4049	$155.40	$155.40	$155.40
Purchase #2	$126.41	5.258%	$133.0566	$133.06	$133.05	$133.10
Purchase #3	$150.30	11.493%	$167.574	$167.57	$167.55	$167.60
Purchase #4	$84.45	7.628%	$90.8918	$90.89	$90.90	$90.90
Purchase #5	$97.54	5.576%	$102.9788	$102.98	$103.00	$103.00
Purchase #6	$200.31	7.421%	$215.175	$215.18	$215.20	$215.20
Purchase #7	$233.35	12.231%	$261.891	$261.89	$261.90	$261.90
7 purchase totals =	$1,032.09		$1,126.9721	$1,126.97	$1,127.00	$1,127.10