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	$140.61	7.217%	$150.7578	$150.76	$150.75	$150.80
Purchase #2	$129.88	4.638%	$135.9038	$135.90	$135.90	$135.90
Purchase #3	$50.71	5.708%	$53.6045	$53.60	$53.60	$53.60
Purchase #4	$98.57	5.604%	$104.0939	$104.09	$104.10	$104.10
Purchase #5	$215.38	11.280%	$239.6749	$239.67	$239.65	$239.70
Purchase #6	$116.76	9.248%	$127.558	$127.56	$127.55	$127.60
Purchase #7	$118.88	10.435%	$131.2851	$131.29	$131.30	$131.30
7 purchase totals =	$870.79		$942.8780	$942.87	$942.85	$943.00