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	$108.71	3.811%	$112.8529	$112.85	$112.85	$112.90
Purchase #2	$78.58	9.638%	$86.1535	$86.15	$86.15	$86.20
Purchase #3	$238.88	10.129%	$263.0762	$263.08	$263.10	$263.10
Purchase #4	$171.28	6.677%	$182.7164	$182.72	$182.70	$182.70
Purchase #5	$211.26	3.155%	$217.9253	$217.93	$217.95	$217.90
Purchase #6	$183.33	11.724%	$204.8236	$204.82	$204.80	$204.80
Purchase #7	$29.72	10.605%	$32.8718	$32.87	$32.85	$32.90
7 purchase totals =	$1,021.76		$1,100.4197	$1,100.42	$1,100.40	$1,100.50