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	$99.92	13.539%	$113.4482	$113.45	$113.45	$113.40
Purchase #2	$244.72	7.176%	$262.2811	$262.28	$262.30	$262.30
Purchase #3	$188.39	13.334%	$213.5099	$213.51	$213.50	$213.50
Purchase #4	$93.44	8.388%	$101.2777	$101.28	$101.30	$101.30
Purchase #5	$182.26	13.221%	$206.3566	$206.36	$206.35	$206.40
Purchase #6	$82.67	4.786%	$86.6266	$86.63	$86.65	$86.60
Purchase #7	$111.93	4.278%	$116.7184	$116.72	$116.70	$116.70
7 purchase totals =	$1,003.33		$1,100.2185	$1,100.23	$1,100.25	$1,100.20