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	$52.33	12.743%	$58.9984	$59.00	$59.00	$59.00
Purchase #2	$214.64	4.122%	$223.4875	$223.49	$223.50	$223.50
Purchase #3	$219.79	10.276%	$242.3756	$242.38	$242.40	$242.40
Purchase #4	$42.80	9.418%	$46.8309	$46.83	$46.85	$46.80
Purchase #5	$168.92	7.410%	$181.437	$181.44	$181.45	$181.40
Purchase #6	$100.98	4.742%	$105.7685	$105.77	$105.75	$105.80
Purchase #7	$120.91	11.466%	$134.7735	$134.77	$134.75	$134.80
7 purchase totals =	$920.37		$993.6714	$993.68	$993.70	$993.70