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	$87.93	12.290%	$98.7366	$98.74	$98.75	$98.70
Purchase #2	$230.53	7.273%	$247.2964	$247.30	$247.30	$247.30
Purchase #3	$162.33	12.433%	$182.5125	$182.51	$182.50	$182.50
Purchase #4	$246.49	3.553%	$255.2478	$255.25	$255.25	$255.20
Purchase #5	$100.90	12.843%	$113.8586	$113.86	$113.85	$113.90
Purchase #6	$81.82	3.270%	$84.4955	$84.50	$84.50	$84.50
Purchase #7	$123.25	6.543%	$131.3142	$131.31	$131.30	$131.30
7 purchase totals =	$1,033.25		$1,113.4616	$1,113.47	$1,113.45	$1,113.40