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	$172.91	5.549%	$182.5048	$182.50	$182.50	$182.50
Purchase #2	$108.69	5.751%	$114.9408	$114.94	$114.95	$114.90
Purchase #3	$217.61	13.653%	$247.3203	$247.32	$247.30	$247.30
Purchase #4	$11.75	9.139%	$12.8238	$12.82	$12.80	$12.80
Purchase #5	$20.52	9.140%	$22.3955	$22.40	$22.40	$22.40
Purchase #6	$155.67	10.418%	$171.8877	$171.89	$171.90	$171.90
Purchase #7	$231.37	10.816%	$256.395	$256.40	$256.40	$256.40
7 purchase totals =	$918.52		$1,008.2679	$1,008.27	$1,008.25	$1,008.20