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	$113.38	4.353%	$118.3154	$118.32	$118.30	$118.30
Purchase #2	$66.39	4.297%	$69.2428	$69.24	$69.25	$69.20
Purchase #3	$115.84	6.817%	$123.7368	$123.74	$123.75	$123.70
Purchase #4	$40.61	5.743%	$42.9422	$42.94	$42.95	$42.90
Purchase #5	$241.94	11.837%	$270.5784	$270.58	$270.60	$270.60
Purchase #6	$189.92	9.764%	$208.4638	$208.46	$208.45	$208.50
Purchase #7	$164.63	11.365%	$183.3402	$183.34	$183.35	$183.30
7 purchase totals =	$932.71		$1,016.6196	$1,016.62	$1,016.65	$1,016.50