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	$57.70	9.757%	$63.3298	$63.33	$63.35	$63.30
Purchase #2	$140.63	6.222%	$149.38	$149.38	$149.40	$149.40
Purchase #3	$29.68	9.808%	$32.591	$32.59	$32.60	$32.60
Purchase #4	$86.97	10.104%	$95.7574	$95.76	$95.75	$95.80
Purchase #5	$72.88	13.172%	$82.4798	$82.48	$82.50	$82.50
Purchase #6	$103.50	9.179%	$113.0003	$113.00	$113.00	$113.00
Purchase #7	$232.30	11.801%	$259.7137	$259.71	$259.70	$259.70
7 purchase totals =	$723.66		$796.2520	$796.25	$796.30	$796.30