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	$180.83	7.483%	$194.3615	$194.36	$194.35	$194.40
Purchase #2	$250.50	6.397%	$266.5245	$266.52	$266.50	$266.50
Purchase #3	$241.56	11.551%	$269.4626	$269.46	$269.45	$269.50
Purchase #4	$238.47	11.199%	$265.1763	$265.18	$265.20	$265.20
Purchase #5	$198.93	12.853%	$224.4985	$224.50	$224.50	$224.50
Purchase #6	$174.93	12.273%	$196.3992	$196.40	$196.40	$196.40
Purchase #7	$247.85	10.193%	$273.1134	$273.11	$273.10	$273.10
7 purchase totals =	$1,533.07		$1,689.5360	$1,689.53	$1,689.50	$1,689.60