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	$217.50	3.206%	$224.4731	$224.47	$224.45	$224.50
Purchase #2	$218.85	3.201%	$225.8554	$225.86	$225.85	$225.90
Purchase #3	$168.70	12.608%	$189.9697	$189.97	$189.95	$190.00
Purchase #4	$184.32	6.841%	$196.9293	$196.93	$196.95	$196.90
Purchase #5	$177.65	6.732%	$189.6094	$189.61	$189.60	$189.60
Purchase #6	$207.65	7.263%	$222.7316	$222.73	$222.75	$222.70
Purchase #7	$87.80	12.788%	$99.0279	$99.03	$99.05	$99.00
7 purchase totals =	$1,262.47		$1,348.5964	$1,348.60	$1,348.60	$1,348.60