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	$231.66	10.257%	$255.4214	$255.42	$255.40	$255.40
Purchase #2	$99.59	5.179%	$104.7478	$104.75	$104.75	$104.70
Purchase #3	$67.71	5.801%	$71.6379	$71.64	$71.65	$71.60
Purchase #4	$128.78	13.828%	$146.5877	$146.59	$146.60	$146.60
Purchase #5	$192.48	6.143%	$204.304	$204.30	$204.30	$204.30
Purchase #6	$195.75	8.207%	$211.8152	$211.82	$211.80	$211.80
Purchase #7	$127.79	6.636%	$136.2701	$136.27	$136.25	$136.30
7 purchase totals =	$1,043.76		$1,130.7841	$1,130.79	$1,130.75	$1,130.70