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	$207.98	11.835%	$232.5944	$232.59	$232.60	$232.60
Purchase #2	$101.49	4.388%	$105.9434	$105.94	$105.95	$105.90
Purchase #3	$197.56	7.272%	$211.9266	$211.93	$211.95	$211.90
Purchase #4	$91.49	9.554%	$100.231	$100.23	$100.25	$100.20
Purchase #5	$31.88	6.794%	$34.0459	$34.05	$34.05	$34.00
Purchase #6	$151.57	5.724%	$160.2459	$160.25	$160.25	$160.20
Purchase #7	$86.36	3.549%	$89.4249	$89.42	$89.40	$89.40
7 purchase totals =	$868.33		$934.4121	$934.41	$934.45	$934.20