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	$239.85	4.511%	$250.6696	$250.67	$250.65	$250.70
Purchase #2	$38.54	4.569%	$40.3009	$40.30	$40.30	$40.30
Purchase #3	$38.85	12.805%	$43.8247	$43.82	$43.80	$43.80
Purchase #4	$202.79	4.339%	$211.5891	$211.59	$211.60	$211.60
Purchase #5	$107.85	7.586%	$116.0315	$116.03	$116.05	$116.00
Purchase #6	$114.78	7.497%	$123.3851	$123.39	$123.40	$123.40
Purchase #7	$119.33	4.828%	$125.0913	$125.09	$125.10	$125.10
7 purchase totals =	$861.99		$910.8922	$910.89	$910.90	$910.90