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	$72.60	12.595%	$81.744	$81.74	$81.75	$81.70
Purchase #2	$72.80	10.245%	$80.2584	$80.26	$80.25	$80.30
Purchase #3	$131.40	4.203%	$136.9227	$136.92	$136.90	$136.90
Purchase #4	$114.26	4.722%	$119.6554	$119.66	$119.65	$119.70
Purchase #5	$225.42	13.569%	$256.0072	$256.01	$256.00	$256.00
Purchase #6	$227.50	13.553%	$258.3331	$258.33	$258.35	$258.30
Purchase #7	$137.32	11.309%	$152.8495	$152.85	$152.85	$152.80
7 purchase totals =	$981.30		$1,085.7703	$1,085.77	$1,085.75	$1,085.70