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	$186.35	5.489%	$196.5788	$196.58	$196.60	$196.60
Purchase #2	$74.83	9.715%	$82.0997	$82.10	$82.10	$82.10
Purchase #3	$182.34	7.271%	$195.5979	$195.60	$195.60	$195.60
Purchase #4	$200.35	13.328%	$227.0526	$227.05	$227.05	$227.10
Purchase #5	$51.66	5.767%	$54.6392	$54.64	$54.65	$54.60
Purchase #6	$39.99	7.359%	$42.9329	$42.93	$42.95	$42.90
Purchase #7	$122.63	11.844%	$137.1543	$137.15	$137.15	$137.20
7 purchase totals =	$858.15		$936.0554	$936.05	$936.10	$936.10