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	$233.56	9.428%	$255.58	$255.58	$255.60	$255.60
Purchase #2	$141.93	5.717%	$150.0441	$150.04	$150.05	$150.00
Purchase #3	$76.47	3.724%	$79.3177	$79.32	$79.30	$79.30
Purchase #4	$70.81	4.391%	$73.9193	$73.92	$73.90	$73.90
Purchase #5	$133.63	12.677%	$150.5703	$150.57	$150.55	$150.60
Purchase #6	$144.79	6.523%	$154.2347	$154.23	$154.25	$154.20
Purchase #7	$189.67	4.113%	$197.4711	$197.47	$197.45	$197.50
7 purchase totals =	$990.86		$1,061.1372	$1,061.13	$1,061.10	$1,061.10