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	$222.32	12.387%	$249.8588	$249.86	$249.85	$249.90
Purchase #2	$30.75	3.840%	$31.9308	$31.93	$31.95	$31.90
Purchase #3	$37.40	7.628%	$40.2529	$40.25	$40.25	$40.30
Purchase #4	$78.32	12.230%	$87.8985	$87.90	$87.90	$87.90
Purchase #5	$208.64	12.847%	$235.444	$235.44	$235.45	$235.40
Purchase #6	$233.44	12.158%	$261.8216	$261.82	$261.80	$261.80
Purchase #7	$112.83	4.729%	$118.1657	$118.17	$118.15	$118.20
7 purchase totals =	$923.70		$1,025.3723	$1,025.37	$1,025.35	$1,025.40