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	$196.97	13.242%	$223.0528	$223.05	$223.05	$223.10
Purchase #2	$213.67	10.738%	$236.6139	$236.61	$236.60	$236.60
Purchase #3	$96.58	8.604%	$104.8897	$104.89	$104.90	$104.90
Purchase #4	$62.60	10.712%	$69.3057	$69.31	$69.30	$69.30
Purchase #5	$100.60	12.113%	$112.7857	$112.79	$112.80	$112.80
Purchase #6	$50.28	3.210%	$51.894	$51.89	$51.90	$51.90
Purchase #7	$135.78	7.373%	$145.7911	$145.79	$145.80	$145.80
7 purchase totals =	$856.48		$944.3329	$944.33	$944.35	$944.40