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	$135.83	9.127%	$148.2272	$148.23	$148.25	$148.20
Purchase #2	$7.35	6.378%	$7.8188	$7.82	$7.80	$7.80
Purchase #3	$36.93	11.476%	$41.1681	$41.17	$41.15	$41.20
Purchase #4	$48.72	11.587%	$54.3652	$54.37	$54.35	$54.40
Purchase #5	$248.34	4.301%	$259.0211	$259.02	$259.00	$259.00
Purchase #6	$43.89	9.549%	$48.0811	$48.08	$48.10	$48.10
Purchase #7	$210.36	5.775%	$222.5083	$222.51	$222.50	$222.50
7 purchase totals =	$731.42		$781.1898	$781.20	$781.15	$781.20