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	$94.37	5.418%	$99.483	$99.48	$99.50	$99.50
Purchase #2	$72.86	4.783%	$76.3449	$76.34	$76.35	$76.30
Purchase #3	$115.25	5.165%	$121.2027	$121.20	$121.20	$121.20
Purchase #4	$185.53	6.130%	$196.903	$196.90	$196.90	$196.90
Purchase #5	$241.56	10.509%	$266.9455	$266.95	$266.95	$266.90
Purchase #6	$198.52	6.721%	$211.8625	$211.86	$211.85	$211.90
Purchase #7	$117.76	7.314%	$126.373	$126.37	$126.35	$126.40
7 purchase totals =	$1,025.85		$1,099.1146	$1,099.10	$1,099.10	$1,099.10