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	$78.41	10.806%	$86.883	$86.88	$86.90	$86.90
Purchase #2	$32.78	5.338%	$34.5298	$34.53	$34.55	$34.50
Purchase #3	$56.98	11.218%	$63.372	$63.37	$63.35	$63.40
Purchase #4	$224.62	13.592%	$255.1504	$255.15	$255.15	$255.20
Purchase #5	$39.81	9.254%	$43.494	$43.49	$43.50	$43.50
Purchase #6	$197.44	12.396%	$221.9147	$221.91	$221.90	$221.90
Purchase #7	$25.30	10.116%	$27.8593	$27.86	$27.85	$27.90
7 purchase totals =	$655.34		$733.2032	$733.19	$733.20	$733.30