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	$87.83	12.319%	$98.6498	$98.65	$98.65	$98.60
Purchase #2	$136.82	9.715%	$150.1121	$150.11	$150.10	$150.10
Purchase #3	$40.89	8.637%	$44.4217	$44.42	$44.40	$44.40
Purchase #4	$186.60	11.726%	$208.4807	$208.48	$208.50	$208.50
Purchase #5	$179.46	5.348%	$189.0575	$189.06	$189.05	$189.10
Purchase #6	$54.57	8.268%	$59.0818	$59.08	$59.10	$59.10
Purchase #7	$42.63	9.384%	$46.6304	$46.63	$46.65	$46.60
7 purchase totals =	$728.80		$796.4340	$796.43	$796.45	$796.40