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	$8.81	8.118%	$9.5252	$9.53	$9.55	$9.50
Purchase #2	$195.32	11.575%	$217.9283	$217.93	$217.95	$217.90
Purchase #3	$204.49	8.790%	$222.4647	$222.46	$222.45	$222.50
Purchase #4	$167.31	10.423%	$184.7487	$184.75	$184.75	$184.70
Purchase #5	$193.76	12.769%	$218.5012	$218.50	$218.50	$218.50
Purchase #6	$125.57	4.790%	$131.5848	$131.58	$131.60	$131.60
Purchase #7	$88.50	3.636%	$91.7179	$91.72	$91.70	$91.70
7 purchase totals =	$983.76		$1,076.4708	$1,076.47	$1,076.50	$1,076.40