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	$207.89	3.337%	$214.8273	$214.83	$214.85	$214.80
Purchase #2	$131.45	13.743%	$149.5152	$149.52	$149.50	$149.50
Purchase #3	$46.26	11.615%	$51.6331	$51.63	$51.65	$51.60
Purchase #4	$71.56	13.627%	$81.3115	$81.31	$81.30	$81.30
Purchase #5	$215.37	13.872%	$245.2461	$245.25	$245.25	$245.20
Purchase #6	$243.27	12.855%	$274.5424	$274.54	$274.55	$274.50
Purchase #7	$102.90	11.285%	$114.5123	$114.51	$114.50	$114.50
7 purchase totals =	$1,018.70		$1,131.5879	$1,131.59	$1,131.60	$1,131.40