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	$170.38	9.715%	$186.9324	$186.93	$186.95	$186.90
Purchase #2	$161.75	4.188%	$168.5241	$168.52	$168.50	$168.50
Purchase #3	$107.77	9.577%	$118.0911	$118.09	$118.10	$118.10
Purchase #4	$104.72	9.206%	$114.3605	$114.36	$114.35	$114.40
Purchase #5	$73.93	4.782%	$77.4653	$77.47	$77.45	$77.50
Purchase #6	$208.46	5.203%	$219.3062	$219.31	$219.30	$219.30
Purchase #7	$213.52	3.434%	$220.8523	$220.85	$220.85	$220.90
7 purchase totals =	$1,040.53		$1,105.5319	$1,105.53	$1,105.50	$1,105.60