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	$200.85	4.281%	$209.4484	$209.45	$209.45	$209.40
Purchase #2	$190.35	4.600%	$199.1061	$199.11	$199.10	$199.10
Purchase #3	$45.37	8.767%	$49.3476	$49.35	$49.35	$49.30
Purchase #4	$126.81	10.274%	$139.8385	$139.84	$139.85	$139.80
Purchase #5	$119.41	10.381%	$131.806	$131.81	$131.80	$131.80
Purchase #6	$168.93	9.658%	$185.2453	$185.25	$185.25	$185.20
Purchase #7	$144.63	11.589%	$161.3912	$161.39	$161.40	$161.40
7 purchase totals =	$996.35		$1,076.1831	$1,076.20	$1,076.20	$1,076.00