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	$103.99	5.186%	$109.3829	$109.38	$109.40	$109.40
Purchase #2	$187.39	4.753%	$196.2966	$196.30	$196.30	$196.30
Purchase #3	$132.69	8.118%	$143.4618	$143.46	$143.45	$143.50
Purchase #4	$130.48	6.489%	$138.9468	$138.95	$138.95	$138.90
Purchase #5	$82.96	4.341%	$86.5613	$86.56	$86.55	$86.60
Purchase #6	$154.76	12.640%	$174.3217	$174.32	$174.30	$174.30
Purchase #7	$144.82	10.490%	$160.0116	$160.01	$160.00	$160.00
7 purchase totals =	$937.09		$1,008.9827	$1,008.98	$1,008.95	$1,009.00