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	$235.96	10.714%	$261.2408	$261.24	$261.25	$261.20
Purchase #2	$140.88	6.498%	$150.0344	$150.03	$150.05	$150.00
Purchase #3	$92.30	4.504%	$96.4572	$96.46	$96.45	$96.50
Purchase #4	$21.27	10.606%	$23.5259	$23.53	$23.55	$23.50
Purchase #5	$108.82	10.691%	$120.4539	$120.45	$120.45	$120.50
Purchase #6	$103.40	6.796%	$110.4271	$110.43	$110.45	$110.40
Purchase #7	$242.66	5.472%	$255.9384	$255.94	$255.95	$255.90
7 purchase totals =	$945.29		$1,018.0777	$1,018.08	$1,018.15	$1,018.00