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	$97.83	7.259%	$104.9315	$104.93	$104.95	$104.90
Purchase #2	$219.37	9.206%	$239.5652	$239.57	$239.55	$239.60
Purchase #3	$228.31	11.847%	$255.3579	$255.36	$255.35	$255.40
Purchase #4	$76.45	3.111%	$78.8284	$78.83	$78.85	$78.80
Purchase #5	$163.73	11.697%	$182.8815	$182.88	$182.90	$182.90
Purchase #6	$184.49	6.210%	$195.9468	$195.95	$195.95	$195.90
Purchase #7	$149.80	10.134%	$164.9807	$164.98	$165.00	$165.00
7 purchase totals =	$1,119.98		$1,222.4920	$1,222.50	$1,222.55	$1,222.50