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	$95.69	8.715%	$104.0294	$104.03	$104.05	$104.00
Purchase #2	$198.69	11.318%	$221.1777	$221.18	$221.20	$221.20
Purchase #3	$112.34	13.644%	$127.6677	$127.67	$127.65	$127.70
Purchase #4	$55.41	11.635%	$61.857	$61.86	$61.85	$61.90
Purchase #5	$193.82	7.689%	$208.7228	$208.72	$208.70	$208.70
Purchase #6	$61.47	3.441%	$63.5852	$63.59	$63.60	$63.60
Purchase #7	$36.63	12.746%	$41.2989	$41.30	$41.30	$41.30
7 purchase totals =	$754.05		$828.3387	$828.35	$828.35	$828.40