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	$17.45	10.620%	$19.3032	$19.30	$19.30	$19.30
Purchase #2	$59.85	6.161%	$63.5374	$63.54	$63.55	$63.50
Purchase #3	$59.55	7.730%	$64.1532	$64.15	$64.15	$64.20
Purchase #4	$82.52	8.492%	$89.5276	$89.53	$89.55	$89.50
Purchase #5	$199.98	12.310%	$224.5975	$224.60	$224.60	$224.60
Purchase #6	$72.35	13.808%	$82.3401	$82.34	$82.35	$82.30
Purchase #7	$163.39	11.533%	$182.2338	$182.23	$182.25	$182.20
7 purchase totals =	$655.09		$725.6928	$725.69	$725.75	$725.60