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	$137.33	10.820%	$152.1891	$152.19	$152.20	$152.20
Purchase #2	$141.70	6.443%	$150.8297	$150.83	$150.85	$150.80
Purchase #3	$237.42	10.770%	$262.9901	$262.99	$263.00	$263.00
Purchase #4	$51.33	6.765%	$54.8025	$54.80	$54.80	$54.80
Purchase #5	$43.48	13.759%	$49.4624	$49.46	$49.45	$49.50
Purchase #6	$39.72	8.771%	$43.2038	$43.20	$43.20	$43.20
Purchase #7	$228.38	4.604%	$238.8946	$238.89	$238.90	$238.90
7 purchase totals =	$879.36		$952.3722	$952.36	$952.40	$952.40