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	$211.82	12.572%	$238.45	$238.45	$238.45	$238.50
Purchase #2	$189.82	5.863%	$200.9491	$200.95	$200.95	$200.90
Purchase #3	$71.70	6.611%	$76.4401	$76.44	$76.45	$76.40
Purchase #4	$164.40	10.838%	$182.2177	$182.22	$182.20	$182.20
Purchase #5	$49.32	7.460%	$52.9993	$53.00	$53.00	$53.00
Purchase #6	$20.45	10.421%	$22.5811	$22.58	$22.60	$22.60
Purchase #7	$217.93	4.725%	$228.2272	$228.23	$228.25	$228.20
7 purchase totals =	$925.44		$1,001.8645	$1,001.87	$1,001.90	$1,001.80