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	$77.56	10.791%	$85.9295	$85.93	$85.95	$85.90
Purchase #2	$209.73	8.152%	$226.8272	$226.83	$226.85	$226.80
Purchase #3	$188.66	12.495%	$212.2331	$212.23	$212.25	$212.20
Purchase #4	$205.76	10.575%	$227.5191	$227.52	$227.50	$227.50
Purchase #5	$203.82	9.104%	$222.3758	$222.38	$222.40	$222.40
Purchase #6	$117.31	11.832%	$131.1901	$131.19	$131.20	$131.20
Purchase #7	$45.74	8.162%	$49.4733	$49.47	$49.45	$49.50
7 purchase totals =	$1,048.58		$1,155.5481	$1,155.55	$1,155.60	$1,155.50