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	$150.86	10.434%	$166.6007	$166.60	$166.60	$166.60
Purchase #2	$64.83	4.265%	$67.595	$67.60	$67.60	$67.60
Purchase #3	$103.98	11.143%	$115.5665	$115.57	$115.55	$115.60
Purchase #4	$209.30	11.233%	$232.8107	$232.81	$232.80	$232.80
Purchase #5	$153.57	12.582%	$172.8922	$172.89	$172.90	$172.90
Purchase #6	$178.92	11.586%	$199.6497	$199.65	$199.65	$199.60
Purchase #7	$109.32	9.567%	$119.7786	$119.78	$119.80	$119.80
7 purchase totals =	$970.78		$1,074.8934	$1,074.90	$1,074.90	$1,074.90