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	$241.86	4.611%	$253.0122	$253.01	$253.00	$253.00
Purchase #2	$118.85	12.491%	$133.6956	$133.70	$133.70	$133.70
Purchase #3	$72.48	8.661%	$78.7575	$78.76	$78.75	$78.80
Purchase #4	$76.58	7.520%	$82.3388	$82.34	$82.35	$82.30
Purchase #5	$103.85	12.737%	$117.0774	$117.08	$117.10	$117.10
Purchase #6	$195.73	8.145%	$211.6722	$211.67	$211.65	$211.70
Purchase #7	$155.93	6.191%	$165.5836	$165.58	$165.60	$165.60
7 purchase totals =	$965.28		$1,042.1373	$1,042.14	$1,042.15	$1,042.20