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	$215.59	11.393%	$240.1522	$240.15	$240.15	$240.20
Purchase #2	$126.62	4.108%	$131.8215	$131.82	$131.80	$131.80
Purchase #3	$211.36	7.485%	$227.1803	$227.18	$227.20	$227.20
Purchase #4	$20.33	12.633%	$22.8983	$22.90	$22.90	$22.90
Purchase #5	$241.60	13.615%	$274.4938	$274.49	$274.50	$274.50
Purchase #6	$209.25	6.168%	$222.1565	$222.16	$222.15	$222.20
Purchase #7	$144.85	5.585%	$152.9399	$152.94	$152.95	$152.90
7 purchase totals =	$1,169.60		$1,271.6425	$1,271.64	$1,271.65	$1,271.70