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	$204.50	4.334%	$213.363	$213.36	$213.35	$213.40
Purchase #2	$115.92	13.254%	$131.284	$131.28	$131.30	$131.30
Purchase #3	$136.75	7.411%	$146.8845	$146.88	$146.90	$146.90
Purchase #4	$73.46	9.778%	$80.6429	$80.64	$80.65	$80.60
Purchase #5	$244.88	4.721%	$256.4408	$256.44	$256.45	$256.40
Purchase #6	$201.52	5.265%	$212.13	$212.13	$212.15	$212.10
Purchase #7	$250.83	11.517%	$279.7181	$279.72	$279.70	$279.70
7 purchase totals =	$1,227.86		$1,320.4633	$1,320.45	$1,320.50	$1,320.40