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	$60.46	8.312%	$65.4854	$65.49	$65.50	$65.50
Purchase #2	$233.47	12.165%	$261.8716	$261.87	$261.85	$261.90
Purchase #3	$212.86	10.831%	$235.9149	$235.91	$235.90	$235.90
Purchase #4	$72.62	9.774%	$79.7179	$79.72	$79.70	$79.70
Purchase #5	$85.59	8.166%	$92.5793	$92.58	$92.60	$92.60
Purchase #6	$156.73	7.508%	$168.4973	$168.50	$168.50	$168.50
Purchase #7	$59.27	5.161%	$62.3289	$62.33	$62.35	$62.30
7 purchase totals =	$881.00		$966.3953	$966.40	$966.40	$966.40