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	$114.63	12.384%	$128.8258	$128.83	$128.85	$128.80
Purchase #2	$99.30	12.265%	$111.4791	$111.48	$111.50	$111.50
Purchase #3	$5.60	11.136%	$6.2236	$6.22	$6.20	$6.20
Purchase #4	$61.89	6.411%	$65.8578	$65.86	$65.85	$65.90
Purchase #5	$83.98	8.143%	$90.8185	$90.82	$90.80	$90.80
Purchase #6	$206.69	11.715%	$230.9037	$230.90	$230.90	$230.90
Purchase #7	$61.76	9.154%	$67.4135	$67.41	$67.40	$67.40
7 purchase totals =	$633.85		$701.5220	$701.52	$701.50	$701.50