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	$76.49	11.140%	$85.011	$85.01	$85.00	$85.00
Purchase #2	$221.37	4.781%	$231.9537	$231.95	$231.95	$232.00
Purchase #3	$81.49	5.602%	$86.0551	$86.06	$86.05	$86.10
Purchase #4	$86.58	3.143%	$89.3012	$89.30	$89.30	$89.30
Purchase #5	$126.51	11.581%	$141.1611	$141.16	$141.15	$141.20
Purchase #6	$126.58	13.745%	$143.9784	$143.98	$144.00	$144.00
Purchase #7	$182.30	4.720%	$190.9046	$190.90	$190.90	$190.90
7 purchase totals =	$901.32		$968.3651	$968.36	$968.35	$968.50