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	$57.90	8.733%	$62.9564	$62.96	$62.95	$63.00
Purchase #2	$52.31	3.545%	$54.1644	$54.16	$54.15	$54.20
Purchase #3	$63.84	11.712%	$71.3169	$71.32	$71.30	$71.30
Purchase #4	$94.98	8.658%	$103.2034	$103.20	$103.20	$103.20
Purchase #5	$245.85	10.254%	$271.0595	$271.06	$271.05	$271.10
Purchase #6	$28.31	11.266%	$31.4994	$31.50	$31.50	$31.50
Purchase #7	$161.32	3.856%	$167.5405	$167.54	$167.55	$167.50
7 purchase totals =	$704.51		$761.7405	$761.74	$761.70	$761.80