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	$106.35	11.557%	$118.6409	$118.64	$118.65	$118.60
Purchase #2	$178.93	11.245%	$199.0507	$199.05	$199.05	$199.10
Purchase #3	$136.68	4.280%	$142.5299	$142.53	$142.55	$142.50
Purchase #4	$38.45	9.381%	$42.057	$42.06	$42.05	$42.10
Purchase #5	$96.44	4.302%	$100.5888	$100.59	$100.60	$100.60
Purchase #6	$125.74	11.298%	$139.9461	$139.95	$139.95	$139.90
Purchase #7	$241.38	5.598%	$254.8925	$254.89	$254.90	$254.90
7 purchase totals =	$923.97		$997.7059	$997.71	$997.75	$997.70