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	$6.94	13.179%	$7.8546	$7.85	$7.85	$7.90
Purchase #2	$153.28	6.193%	$162.7726	$162.77	$162.75	$162.80
Purchase #3	$104.47	7.610%	$112.4202	$112.42	$112.40	$112.40
Purchase #4	$43.32	6.643%	$46.1977	$46.20	$46.20	$46.20
Purchase #5	$161.57	6.850%	$172.6375	$172.64	$172.65	$172.60
Purchase #6	$164.51	6.437%	$175.0995	$175.10	$175.10	$175.10
Purchase #7	$85.56	11.758%	$95.6201	$95.62	$95.60	$95.60
7 purchase totals =	$719.65		$772.6022	$772.60	$772.55	$772.60