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	$38.66	12.387%	$43.4488	$43.45	$43.45	$43.40
Purchase #2	$191.71	4.367%	$200.082	$200.08	$200.10	$200.10
Purchase #3	$198.97	11.726%	$222.3012	$222.30	$222.30	$222.30
Purchase #4	$168.37	5.672%	$177.9199	$177.92	$177.90	$177.90
Purchase #5	$202.99	10.870%	$225.055	$225.06	$225.05	$225.10
Purchase #6	$82.40	4.522%	$86.1261	$86.13	$86.15	$86.10
Purchase #7	$63.45	11.786%	$70.9282	$70.93	$70.95	$70.90
7 purchase totals =	$946.55		$1,025.8612	$1,025.87	$1,025.90	$1,025.80