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	$156.38	10.576%	$172.9187	$172.92	$172.90	$172.90
Purchase #2	$5.49	11.849%	$6.1405	$6.14	$6.15	$6.10
Purchase #3	$242.58	8.153%	$262.3575	$262.36	$262.35	$262.40
Purchase #4	$176.53	12.424%	$198.4621	$198.46	$198.45	$198.50
Purchase #5	$169.97	6.526%	$181.0622	$181.06	$181.05	$181.10
Purchase #6	$117.89	8.270%	$127.6395	$127.64	$127.65	$127.60
Purchase #7	$83.47	10.235%	$92.0132	$92.01	$92.00	$92.00
7 purchase totals =	$952.31		$1,040.5937	$1,040.59	$1,040.55	$1,040.60