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	$137.52	7.818%	$148.2713	$148.27	$148.25	$148.30
Purchase #2	$134.53	5.562%	$142.0126	$142.01	$142.00	$142.00
Purchase #3	$145.62	6.665%	$155.3256	$155.33	$155.35	$155.30
Purchase #4	$199.79	11.511%	$222.7878	$222.79	$222.80	$222.80
Purchase #5	$134.77	6.690%	$143.7861	$143.79	$143.80	$143.80
Purchase #6	$220.43	8.184%	$238.47	$238.47	$238.45	$238.50
Purchase #7	$86.47	9.803%	$94.9467	$94.95	$94.95	$94.90
7 purchase totals =	$1,059.13		$1,145.6001	$1,145.61	$1,145.60	$1,145.60