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	$55.64	11.363%	$61.9624	$61.96	$61.95	$62.00
Purchase #2	$194.63	13.479%	$220.8642	$220.86	$220.85	$220.90
Purchase #3	$53.43	11.410%	$59.5264	$59.53	$59.55	$59.50
Purchase #4	$199.86	6.209%	$212.2693	$212.27	$212.25	$212.30
Purchase #5	$163.51	3.380%	$169.0366	$169.04	$169.05	$169.00
Purchase #6	$39.54	8.586%	$42.9349	$42.93	$42.95	$42.90
Purchase #7	$15.81	10.227%	$17.4269	$17.43	$17.45	$17.40
7 purchase totals =	$722.42		$784.0207	$784.02	$784.05	$784.00