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	$112.59	4.152%	$117.2647	$117.26	$117.25	$117.30
Purchase #2	$194.74	12.288%	$218.6697	$218.67	$218.65	$218.70
Purchase #3	$211.89	4.243%	$220.8805	$220.88	$220.90	$220.90
Purchase #4	$89.72	11.243%	$99.8072	$99.81	$99.80	$99.80
Purchase #5	$198.81	6.576%	$211.8837	$211.88	$211.90	$211.90
Purchase #6	$245.61	7.705%	$264.5343	$264.53	$264.55	$264.50
Purchase #7	$217.47	4.781%	$227.8672	$227.87	$227.85	$227.90
7 purchase totals =	$1,270.83		$1,360.9073	$1,360.90	$1,360.90	$1,361.00