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	$55.73	13.838%	$63.4419	$63.44	$63.45	$63.40
Purchase #2	$142.32	13.287%	$161.2301	$161.23	$161.25	$161.20
Purchase #3	$184.60	13.367%	$209.2755	$209.28	$209.30	$209.30
Purchase #4	$85.59	11.549%	$95.4748	$95.47	$95.45	$95.50
Purchase #5	$182.64	12.758%	$205.9412	$205.94	$205.95	$205.90
Purchase #6	$73.85	11.250%	$82.1581	$82.16	$82.15	$82.20
Purchase #7	$169.25	6.207%	$179.7553	$179.76	$179.75	$179.80
7 purchase totals =	$893.98		$997.2769	$997.28	$997.30	$997.30