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	$18.52	4.538%	$19.3604	$19.36	$19.35	$19.40
Purchase #2	$229.37	5.230%	$241.3661	$241.37	$241.35	$241.40
Purchase #3	$100.57	10.245%	$110.8734	$110.87	$110.85	$110.90
Purchase #4	$132.55	8.268%	$143.5092	$143.51	$143.50	$143.50
Purchase #5	$216.90	8.565%	$235.4775	$235.48	$235.50	$235.50
Purchase #6	$74.88	10.648%	$82.8532	$82.85	$82.85	$82.90
Purchase #7	$205.99	3.682%	$213.5746	$213.57	$213.55	$213.60
7 purchase totals =	$978.78		$1,047.0144	$1,047.01	$1,046.95	$1,047.20