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	$181.61	12.280%	$203.9117	$203.91	$203.90	$203.90
Purchase #2	$54.94	11.721%	$61.3795	$61.38	$61.40	$61.40
Purchase #3	$128.68	11.435%	$143.3946	$143.39	$143.40	$143.40
Purchase #4	$179.66	13.510%	$203.9321	$203.93	$203.95	$203.90
Purchase #5	$37.80	6.339%	$40.1961	$40.20	$40.20	$40.20
Purchase #6	$240.88	6.568%	$256.701	$256.70	$256.70	$256.70
Purchase #7	$85.89	8.574%	$93.2542	$93.25	$93.25	$93.30
7 purchase totals =	$909.46		$1,002.7692	$1,002.76	$1,002.80	$1,002.80