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	$38.92	11.355%	$43.3394	$43.34	$43.35	$43.30
Purchase #2	$217.29	3.319%	$224.5019	$224.50	$224.50	$224.50
Purchase #3	$42.44	10.476%	$46.886	$46.89	$46.90	$46.90
Purchase #4	$212.57	8.757%	$231.1848	$231.18	$231.20	$231.20
Purchase #5	$108.79	6.522%	$115.8853	$115.89	$115.90	$115.90
Purchase #6	$239.82	10.474%	$264.9387	$264.94	$264.95	$264.90
Purchase #7	$139.64	13.788%	$158.8936	$158.89	$158.90	$158.90
7 purchase totals =	$999.47		$1,085.6297	$1,085.63	$1,085.70	$1,085.60