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	$214.58	3.691%	$222.5001	$222.50	$222.50	$222.50
Purchase #2	$94.54	9.676%	$103.6877	$103.69	$103.70	$103.70
Purchase #3	$30.67	9.144%	$33.4745	$33.47	$33.45	$33.50
Purchase #4	$175.57	12.635%	$197.7533	$197.75	$197.75	$197.80
Purchase #5	$80.73	13.357%	$91.5131	$91.51	$91.50	$91.50
Purchase #6	$103.88	13.362%	$117.7604	$117.76	$117.75	$117.80
Purchase #7	$228.50	5.120%	$240.1992	$240.20	$240.20	$240.20
7 purchase totals =	$928.47		$1,006.8883	$1,006.88	$1,006.85	$1,007.00