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	$232.55	4.433%	$242.8589	$242.86	$242.85	$242.90
Purchase #2	$101.57	11.549%	$113.3003	$113.30	$113.30	$113.30
Purchase #3	$9.92	8.701%	$10.7831	$10.78	$10.80	$10.80
Purchase #4	$234.31	10.700%	$259.3812	$259.38	$259.40	$259.40
Purchase #5	$37.87	4.314%	$39.5037	$39.50	$39.50	$39.50
Purchase #6	$206.50	9.584%	$226.291	$226.29	$226.30	$226.30
Purchase #7	$100.86	4.596%	$105.4955	$105.50	$105.50	$105.50
7 purchase totals =	$923.58		$997.6137	$997.61	$997.65	$997.70