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	$58.77	8.804%	$63.9441	$63.94	$63.95	$63.90
Purchase #2	$192.65	11.811%	$215.4039	$215.40	$215.40	$215.40
Purchase #3	$136.47	4.612%	$142.764	$142.76	$142.75	$142.80
Purchase #4	$98.34	11.521%	$109.6698	$109.67	$109.65	$109.70
Purchase #5	$154.61	7.713%	$166.5351	$166.54	$166.55	$166.50
Purchase #6	$123.59	4.223%	$128.8092	$128.81	$128.80	$128.80
Purchase #7	$13.76	5.266%	$14.4846	$14.48	$14.50	$14.50
7 purchase totals =	$778.19		$841.6107	$841.60	$841.60	$841.60