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	$93.60	11.780%	$104.6261	$104.63	$104.65	$104.60
Purchase #2	$101.82	5.835%	$107.7612	$107.76	$107.75	$107.80
Purchase #3	$133.61	6.226%	$141.9286	$141.93	$141.95	$141.90
Purchase #4	$233.82	7.581%	$251.5459	$251.55	$251.55	$251.50
Purchase #5	$98.77	13.190%	$111.7978	$111.80	$111.80	$111.80
Purchase #6	$187.61	6.104%	$199.0617	$199.06	$199.05	$199.10
Purchase #7	$138.25	3.143%	$142.5952	$142.60	$142.60	$142.60
7 purchase totals =	$987.48		$1,059.3165	$1,059.33	$1,059.35	$1,059.30