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	$198.32	11.121%	$220.3752	$220.38	$220.40	$220.40
Purchase #2	$75.46	9.348%	$82.514	$82.51	$82.50	$82.50
Purchase #3	$168.29	11.600%	$187.8116	$187.81	$187.80	$187.80
Purchase #4	$64.33	3.462%	$66.5571	$66.56	$66.55	$66.60
Purchase #5	$211.56	13.684%	$240.5099	$240.51	$240.50	$240.50
Purchase #6	$188.38	4.780%	$197.3846	$197.38	$197.40	$197.40
Purchase #7	$38.56	6.291%	$40.9858	$40.99	$41.00	$41.00
7 purchase totals =	$944.90		$1,036.1382	$1,036.14	$1,036.15	$1,036.20