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	$210.81	13.549%	$239.3726	$239.37	$239.35	$239.40
Purchase #2	$202.86	9.669%	$222.4745	$222.47	$222.45	$222.50
Purchase #3	$71.42	10.459%	$78.8898	$78.89	$78.90	$78.90
Purchase #4	$82.37	12.267%	$92.4743	$92.47	$92.45	$92.50
Purchase #5	$25.66	11.156%	$28.5226	$28.52	$28.50	$28.50
Purchase #6	$159.69	5.627%	$168.6758	$168.68	$168.70	$168.70
Purchase #7	$242.76	13.166%	$274.7218	$274.72	$274.70	$274.70
7 purchase totals =	$995.57		$1,105.1314	$1,105.12	$1,105.05	$1,105.20