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	$191.61	12.552%	$215.6609	$215.66	$215.65	$215.70
Purchase #2	$191.26	10.136%	$210.6461	$210.65	$210.65	$210.60
Purchase #3	$137.50	3.850%	$142.7938	$142.79	$142.80	$142.80
Purchase #4	$51.64	5.529%	$54.4952	$54.50	$54.50	$54.50
Purchase #5	$164.57	6.201%	$174.775	$174.78	$174.80	$174.80
Purchase #6	$124.49	12.103%	$139.557	$139.56	$139.55	$139.60
Purchase #7	$106.60	5.861%	$112.8478	$112.85	$112.85	$112.80
7 purchase totals =	$967.67		$1,050.7758	$1,050.79	$1,050.80	$1,050.80