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	$244.84	9.471%	$268.0288	$268.03	$268.05	$268.00
Purchase #2	$136.90	4.791%	$143.4589	$143.46	$143.45	$143.50
Purchase #3	$48.82	11.437%	$54.4035	$54.40	$54.40	$54.40
Purchase #4	$60.52	11.280%	$67.3467	$67.35	$67.35	$67.30
Purchase #5	$163.88	5.111%	$172.2559	$172.26	$172.25	$172.30
Purchase #6	$159.55	13.786%	$181.5456	$181.55	$181.55	$181.50
Purchase #7	$14.40	3.443%	$14.8958	$14.90	$14.90	$14.90
7 purchase totals =	$828.91		$901.9352	$901.95	$901.95	$901.90