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	$110.33	6.645%	$117.6614	$117.66	$117.65	$117.70
Purchase #2	$156.72	5.550%	$165.418	$165.42	$165.40	$165.40
Purchase #3	$81.33	5.663%	$85.9357	$85.94	$85.95	$85.90
Purchase #4	$94.67	4.387%	$98.8232	$98.82	$98.80	$98.80
Purchase #5	$214.93	8.307%	$232.7842	$232.78	$232.80	$232.80
Purchase #6	$59.65	4.758%	$62.4881	$62.49	$62.50	$62.50
Purchase #7	$19.59	4.452%	$20.4621	$20.46	$20.45	$20.50
7 purchase totals =	$737.22		$783.5727	$783.57	$783.55	$783.60